This chapter discusses classification techniques for data mining, including decision trees, Bayes classification, and rule-based classification. It covers the basic process of classification, which involves constructing a model from training data and then using the model to classify new data. Decision tree induction and attribute selection measures like information gain, gain ratio, and Gini index are explained in detail. The chapter also discusses techniques for scaling up classification to large databases, addressing overfitting, and improving accuracy.
The document summarizes key concepts in classification and decision tree induction. It discusses supervised vs unsupervised learning, the two-step classification process of model construction and usage, and decision tree induction basics including attribute selection measures like information gain, gain ratio, and Gini index. It also covers overfitting and techniques like prepruning and postpruning decision trees.
This chapter discusses classification techniques for data mining. It begins with an overview of classification vs unsupervised learning and the basic process of classification which involves model construction using a training set and then using the model to classify new data. It then covers decision trees, describing the basic algorithm for inducing decision trees from data and different measures for attribute selection like information gain, gain ratio, and gini index. The chapter also discusses model evaluation, overfitting, tree pruning, and techniques for scaling classification to large databases.
This document provides an overview of classification techniques in machine learning. It discusses:
- The process of classification involves model construction using a training set and then applying the model to classify new data.
- Supervised learning aims to predict categorical labels while unsupervised learning groups data without labels.
- Popular classification algorithms covered include decision trees, Bayesian classification, and rule-based methods. Attribute selection measures, model evaluation, overfitting, and tree pruning are also discussed.
This document discusses classification and prediction in machine learning. It defines classification as predicting categorical class labels, while prediction models continuous values. The key steps of classification are constructing a model from a training set and using the model to classify new data. Decision trees and rule-based classifiers are described as common classification methods. Attribute selection measures like information gain and gini index are explained for decision tree induction. The document also covers issues in data preparation and model evaluation for classification tasks.
This document discusses various methods for evaluating and improving the accuracy of classification models, including:
- Confusion matrices and measures like accuracy, sensitivity, and precision to evaluate classifier performance.
- Ensemble methods like bagging and boosting that combine multiple models to improve accuracy. Bagging averages predictions from models trained on bootstrap samples, while boosting gives higher weight to instances harder to classify.
- Model selection techniques like statistical tests and ROC curves to compare models and determine the best performing one. ROC curves show the tradeoff between true and false positives for threshold-based classifiers.
Data.Mining.C.6(II).classification and predictionMargaret Wang
The document summarizes different machine learning classification techniques including instance-based approaches, ensemble approaches, co-training approaches, and partially supervised approaches. It discusses k-nearest neighbor classification and how it works. It also explains bagging, boosting, and AdaBoost ensemble methods. Co-training uses two independent views to label unlabeled data. Partially supervised approaches can build classifiers using only positive and unlabeled data.
This document provides a summary of Bayesian classification. Bayesian classification predicts the probability of class membership for new data instances based on prior knowledge and training data. It uses Bayes' theorem to calculate the posterior probability of a class given the attributes of an instance. The naive Bayesian classifier assumes attribute independence and uses frequency counts to estimate probabilities. It classifies new instances by selecting the class with the highest posterior probability. The example shows how probabilities are estimated from training data and used to classify an unseen instance in the play-tennis dataset.
The document summarizes key concepts in classification and decision tree induction. It discusses supervised vs unsupervised learning, the two-step classification process of model construction and usage, and decision tree induction basics including attribute selection measures like information gain, gain ratio, and Gini index. It also covers overfitting and techniques like prepruning and postpruning decision trees.
This chapter discusses classification techniques for data mining. It begins with an overview of classification vs unsupervised learning and the basic process of classification which involves model construction using a training set and then using the model to classify new data. It then covers decision trees, describing the basic algorithm for inducing decision trees from data and different measures for attribute selection like information gain, gain ratio, and gini index. The chapter also discusses model evaluation, overfitting, tree pruning, and techniques for scaling classification to large databases.
This document provides an overview of classification techniques in machine learning. It discusses:
- The process of classification involves model construction using a training set and then applying the model to classify new data.
- Supervised learning aims to predict categorical labels while unsupervised learning groups data without labels.
- Popular classification algorithms covered include decision trees, Bayesian classification, and rule-based methods. Attribute selection measures, model evaluation, overfitting, and tree pruning are also discussed.
This document discusses classification and prediction in machine learning. It defines classification as predicting categorical class labels, while prediction models continuous values. The key steps of classification are constructing a model from a training set and using the model to classify new data. Decision trees and rule-based classifiers are described as common classification methods. Attribute selection measures like information gain and gini index are explained for decision tree induction. The document also covers issues in data preparation and model evaluation for classification tasks.
This document discusses various methods for evaluating and improving the accuracy of classification models, including:
- Confusion matrices and measures like accuracy, sensitivity, and precision to evaluate classifier performance.
- Ensemble methods like bagging and boosting that combine multiple models to improve accuracy. Bagging averages predictions from models trained on bootstrap samples, while boosting gives higher weight to instances harder to classify.
- Model selection techniques like statistical tests and ROC curves to compare models and determine the best performing one. ROC curves show the tradeoff between true and false positives for threshold-based classifiers.
Data.Mining.C.6(II).classification and predictionMargaret Wang
The document summarizes different machine learning classification techniques including instance-based approaches, ensemble approaches, co-training approaches, and partially supervised approaches. It discusses k-nearest neighbor classification and how it works. It also explains bagging, boosting, and AdaBoost ensemble methods. Co-training uses two independent views to label unlabeled data. Partially supervised approaches can build classifiers using only positive and unlabeled data.
This document provides a summary of Bayesian classification. Bayesian classification predicts the probability of class membership for new data instances based on prior knowledge and training data. It uses Bayes' theorem to calculate the posterior probability of a class given the attributes of an instance. The naive Bayesian classifier assumes attribute independence and uses frequency counts to estimate probabilities. It classifies new instances by selecting the class with the highest posterior probability. The example shows how probabilities are estimated from training data and used to classify an unseen instance in the play-tennis dataset.
This document discusses data mining classification and decision trees. It defines classification, provides examples, and discusses techniques like decision trees. It covers decision tree induction processes like determining the best split, measures of impurity, and stopping criteria. It also addresses issues like overfitting, model evaluation methods, and comparing model performance.
This document discusses decision trees, a classification technique in data mining. It defines classification as assigning class labels to unlabeled data based on a training set. Decision trees generate a tree structure to classify data, with internal nodes representing attributes, branches representing attribute values, and leaf nodes holding class labels. An algorithm is used to recursively split the data set into purer subsets based on attribute tests until each subset belongs to a single class. The tree can then classify new examples by traversing it from root to leaf.
Chapter - 6 Data Mining Concepts and Techniques 2nd Ed slides Han & Kambererror007
The document describes Chapter 6 of the book "Data Mining: Concepts and Techniques" which covers the topics of classification and prediction. It defines classification and prediction and discusses key issues in classification such as data preparation, evaluating methods, and decision tree induction. Decision tree induction creates a tree model by recursively splitting the training data on attributes and their values to make predictions. The chapter also covers other classification methods like Bayesian classification, rule-based classification, and support vector machines. It describes the process of model construction from training data and then using the model to classify new, unlabeled data.
This document discusses decision tree induction and attribute selection measures. It describes common measures like information gain, gain ratio, and Gini index that are used to select the best splitting attribute at each node in decision tree construction. It provides examples to illustrate information gain calculation for both discrete and continuous attributes. The document also discusses techniques for handling large datasets like SLIQ and SPRINT that build decision trees in a scalable manner by maintaining attribute value lists.
This document discusses decision trees for data classification. It defines a decision tree as a tree where internal nodes represent attributes, branches represent attribute values, and leaf nodes represent class predictions. It describes the basic decision tree algorithm which builds the tree by recursively splitting the training data on attributes and stopping when data is pure or stopping criteria are met. Finally, it notes advantages like interpretability but also disadvantages like potential overfitting and issues with non-numeric data.
What is the Covering (Rule-based) algorithm?
Classification Rules- Straightforward
1. If-Then rule
2. Generating rules from Decision Tree
Rule-based Algorithm
1. The 1R Algorithm / Learn One Rule
2. The PRISM Algorithm
3. Other Algorithm
Application of Covering algorithm
Discussion on e/m-learning application
The document describes the C4.5 algorithm for building decision trees. It begins with an overview of decision trees and the goals of minimizing tree levels and nodes. It then outlines the steps of the C4.5 algorithm: 1) Choose the attribute that best differentiates training instances, 2) Create a tree node for that attribute and child nodes for each value, 3) Recursively create subordinate nodes until reaching criteria or no remaining attributes. An example applies these steps to build a decision tree to predict customers' responses to a life insurance promotion using attributes like age, income and insurance status.
This document discusses rule-based classification. It describes how rule-based classification models use if-then rules to classify data. It covers extracting rules from decision trees and directly from training data. Key points include using sequential covering algorithms to iteratively learn rules that each cover positive examples of a class, and measuring rule quality based on both coverage and accuracy to determine the best rules.
This document discusses classification and prediction. Classification predicts categorical class labels by classifying data based on a training set and class labels. Prediction models continuous values and predicts unknown values. Some applications are credit approval, marketing, medical diagnosis, and treatment analysis. Classification involves a learning step to describe classes and a classification step to classify new data. Prediction involves estimating accuracy by comparing test results to known labels. Issues with classification and prediction include data preparation, comparing methods, and decision tree induction algorithms.
Based on the decision tree, this case would be classified as follows:
1. Outlook is overcast, so go to the overcast branch
2. For overcast, there are no further tests, so the leaf node is reached
3. The leaf node predicts Play=yes
Therefore, for the given conditions, Play=yes.
A decision tree is a guide to the potential results of a progression of related choices. It permits an individual or association to gauge potential activities against each other dependent on their costs, probabilities, and advantages. They can be utilized either to drive casual conversation or to outline a calculation that predicts the most ideal decision scientifically.
This document provides an overview of decision tree algorithms for machine learning. It discusses key concepts such as:
- Decision trees can be used for classification or regression problems.
- They represent rules that can be understood by humans and used in knowledge systems.
- The trees are built by splitting the data into purer subsets based on attribute tests, using measures like information gain.
- Issues like overfitting are addressed through techniques like reduced error pruning and rule post-pruning.
Introduction to Machine Learning Aristotelis Tsirigos butest
This document provides an introduction to machine learning, covering several key concepts:
- Machine learning aims to build models from data to make predictions without being explicitly programmed.
- There are different types of learning problems including supervised, unsupervised, and reinforcement learning.
- Popular machine learning algorithms discussed include Bayesian learning, nearest neighbors, decision trees, linear classifiers, and ensembles.
- Proper evaluation of machine learning models is important using techniques like cross-validation.
This document discusses classification and prediction techniques in data mining. It covers various classification methods like decision tree induction, Bayesian classification, and support vector machines. It also discusses scaling classification to large databases, evaluating model accuracy, and presenting classification results visually. The key methods covered are decision tree construction using information gain, the naïve Bayesian classifier based on Bayes' theorem, and scaling tree learning using techniques like RainForest.
This document summarizes Chapter 7 of the textbook "Data Mining: Concepts and Techniques" which covers the topics of classification and prediction in data mining. The chapter discusses classification using decision tree induction, Bayesian classification, backpropagation, association rule mining, and other methods. It also addresses evaluating classification methods, handling issues like data preparation and overfitting, and measuring classification accuracy. The goal of classification is to predict categorical class labels, while prediction models continuous values.
Decision trees classify instances by starting at the root node and moving through the tree recursively according to attribute tests at each node, until a leaf node determining the class label is reached. They work by splitting the training data into purer partitions based on the values of predictor attributes, using an attribute selection measure like information gain to choose the splitting attributes. The resulting tree can be pruned to avoid overfitting and reduce error on new data.
Efficient classification of big data using vfdt (very fast decision tree)eSAT Journals
Abstract
Decision Tree learning algorithms have been able to capture knowledge successfully. Decision Trees are best considered when
instances are described by attribute-value pairs and when the target function has a discrete value. The main task of these
decision trees is to use inductive methods to the given values of attributes of an unknown object and determine an
appropriate classification by applying decision tree rules. Decision Trees are very effective forms to evaluate the performance
and represent the algorithms because of their robustness, simplicity, capability of handling numerical and categorical data,
ability to work with large datasets and comprehensibility to a name a few. There are various decision tree algorithms available
like ID3, CART, C4.5, VFDT, QUEST, CTREE, GUIDE, CHAID, CRUISE, etc. In this paper a comparative study on three of
these popular decision tree algorithms - (Iterative Dichotomizer 3), C4.5 which is an evolution of ID3 and VFDT (Very
Fast Decision Tree has been made. An empirical study has been conducted to compare C4.5 and VFDT in terms of accuracy
and execution time and various conclusions have been drawn.
Key Words: Decision tree, ID3, C4.5, VFDT, Information Gain, Gain Ratio, Gini Index, Over−fitting.
This document discusses classification concepts and decision tree induction. It defines classification as predicting categorical class labels based on a training set. Decision tree induction is introduced as a basic classification algorithm that recursively partitions data based on attribute values to construct a tree. Information gain and the Gini index are presented as common measures for selecting the best attribute to use at each tree node split. Overfitting is identified as a potential issue, and prepruning and postpruning techniques are described to address it.
The document discusses classification techniques for supervised learning problems. It describes classification as predicting categorical class labels based on a training set of labeled data. The classification process involves constructing a model from the training set and then using the model to classify new unlabeled data. Common classification techniques discussed include decision tree induction, Bayesian classification methods, and rule-based classification. Model evaluation and techniques for improving accuracy, such as ensemble methods, are also covered.
This document discusses data mining classification and decision trees. It defines classification, provides examples, and discusses techniques like decision trees. It covers decision tree induction processes like determining the best split, measures of impurity, and stopping criteria. It also addresses issues like overfitting, model evaluation methods, and comparing model performance.
This document discusses decision trees, a classification technique in data mining. It defines classification as assigning class labels to unlabeled data based on a training set. Decision trees generate a tree structure to classify data, with internal nodes representing attributes, branches representing attribute values, and leaf nodes holding class labels. An algorithm is used to recursively split the data set into purer subsets based on attribute tests until each subset belongs to a single class. The tree can then classify new examples by traversing it from root to leaf.
Chapter - 6 Data Mining Concepts and Techniques 2nd Ed slides Han & Kambererror007
The document describes Chapter 6 of the book "Data Mining: Concepts and Techniques" which covers the topics of classification and prediction. It defines classification and prediction and discusses key issues in classification such as data preparation, evaluating methods, and decision tree induction. Decision tree induction creates a tree model by recursively splitting the training data on attributes and their values to make predictions. The chapter also covers other classification methods like Bayesian classification, rule-based classification, and support vector machines. It describes the process of model construction from training data and then using the model to classify new, unlabeled data.
This document discusses decision tree induction and attribute selection measures. It describes common measures like information gain, gain ratio, and Gini index that are used to select the best splitting attribute at each node in decision tree construction. It provides examples to illustrate information gain calculation for both discrete and continuous attributes. The document also discusses techniques for handling large datasets like SLIQ and SPRINT that build decision trees in a scalable manner by maintaining attribute value lists.
This document discusses decision trees for data classification. It defines a decision tree as a tree where internal nodes represent attributes, branches represent attribute values, and leaf nodes represent class predictions. It describes the basic decision tree algorithm which builds the tree by recursively splitting the training data on attributes and stopping when data is pure or stopping criteria are met. Finally, it notes advantages like interpretability but also disadvantages like potential overfitting and issues with non-numeric data.
What is the Covering (Rule-based) algorithm?
Classification Rules- Straightforward
1. If-Then rule
2. Generating rules from Decision Tree
Rule-based Algorithm
1. The 1R Algorithm / Learn One Rule
2. The PRISM Algorithm
3. Other Algorithm
Application of Covering algorithm
Discussion on e/m-learning application
The document describes the C4.5 algorithm for building decision trees. It begins with an overview of decision trees and the goals of minimizing tree levels and nodes. It then outlines the steps of the C4.5 algorithm: 1) Choose the attribute that best differentiates training instances, 2) Create a tree node for that attribute and child nodes for each value, 3) Recursively create subordinate nodes until reaching criteria or no remaining attributes. An example applies these steps to build a decision tree to predict customers' responses to a life insurance promotion using attributes like age, income and insurance status.
This document discusses rule-based classification. It describes how rule-based classification models use if-then rules to classify data. It covers extracting rules from decision trees and directly from training data. Key points include using sequential covering algorithms to iteratively learn rules that each cover positive examples of a class, and measuring rule quality based on both coverage and accuracy to determine the best rules.
This document discusses classification and prediction. Classification predicts categorical class labels by classifying data based on a training set and class labels. Prediction models continuous values and predicts unknown values. Some applications are credit approval, marketing, medical diagnosis, and treatment analysis. Classification involves a learning step to describe classes and a classification step to classify new data. Prediction involves estimating accuracy by comparing test results to known labels. Issues with classification and prediction include data preparation, comparing methods, and decision tree induction algorithms.
Based on the decision tree, this case would be classified as follows:
1. Outlook is overcast, so go to the overcast branch
2. For overcast, there are no further tests, so the leaf node is reached
3. The leaf node predicts Play=yes
Therefore, for the given conditions, Play=yes.
A decision tree is a guide to the potential results of a progression of related choices. It permits an individual or association to gauge potential activities against each other dependent on their costs, probabilities, and advantages. They can be utilized either to drive casual conversation or to outline a calculation that predicts the most ideal decision scientifically.
This document provides an overview of decision tree algorithms for machine learning. It discusses key concepts such as:
- Decision trees can be used for classification or regression problems.
- They represent rules that can be understood by humans and used in knowledge systems.
- The trees are built by splitting the data into purer subsets based on attribute tests, using measures like information gain.
- Issues like overfitting are addressed through techniques like reduced error pruning and rule post-pruning.
Introduction to Machine Learning Aristotelis Tsirigos butest
This document provides an introduction to machine learning, covering several key concepts:
- Machine learning aims to build models from data to make predictions without being explicitly programmed.
- There are different types of learning problems including supervised, unsupervised, and reinforcement learning.
- Popular machine learning algorithms discussed include Bayesian learning, nearest neighbors, decision trees, linear classifiers, and ensembles.
- Proper evaluation of machine learning models is important using techniques like cross-validation.
This document discusses classification and prediction techniques in data mining. It covers various classification methods like decision tree induction, Bayesian classification, and support vector machines. It also discusses scaling classification to large databases, evaluating model accuracy, and presenting classification results visually. The key methods covered are decision tree construction using information gain, the naïve Bayesian classifier based on Bayes' theorem, and scaling tree learning using techniques like RainForest.
This document summarizes Chapter 7 of the textbook "Data Mining: Concepts and Techniques" which covers the topics of classification and prediction in data mining. The chapter discusses classification using decision tree induction, Bayesian classification, backpropagation, association rule mining, and other methods. It also addresses evaluating classification methods, handling issues like data preparation and overfitting, and measuring classification accuracy. The goal of classification is to predict categorical class labels, while prediction models continuous values.
Decision trees classify instances by starting at the root node and moving through the tree recursively according to attribute tests at each node, until a leaf node determining the class label is reached. They work by splitting the training data into purer partitions based on the values of predictor attributes, using an attribute selection measure like information gain to choose the splitting attributes. The resulting tree can be pruned to avoid overfitting and reduce error on new data.
Efficient classification of big data using vfdt (very fast decision tree)eSAT Journals
Abstract
Decision Tree learning algorithms have been able to capture knowledge successfully. Decision Trees are best considered when
instances are described by attribute-value pairs and when the target function has a discrete value. The main task of these
decision trees is to use inductive methods to the given values of attributes of an unknown object and determine an
appropriate classification by applying decision tree rules. Decision Trees are very effective forms to evaluate the performance
and represent the algorithms because of their robustness, simplicity, capability of handling numerical and categorical data,
ability to work with large datasets and comprehensibility to a name a few. There are various decision tree algorithms available
like ID3, CART, C4.5, VFDT, QUEST, CTREE, GUIDE, CHAID, CRUISE, etc. In this paper a comparative study on three of
these popular decision tree algorithms - (Iterative Dichotomizer 3), C4.5 which is an evolution of ID3 and VFDT (Very
Fast Decision Tree has been made. An empirical study has been conducted to compare C4.5 and VFDT in terms of accuracy
and execution time and various conclusions have been drawn.
Key Words: Decision tree, ID3, C4.5, VFDT, Information Gain, Gain Ratio, Gini Index, Over−fitting.
This document discusses classification concepts and decision tree induction. It defines classification as predicting categorical class labels based on a training set. Decision tree induction is introduced as a basic classification algorithm that recursively partitions data based on attribute values to construct a tree. Information gain and the Gini index are presented as common measures for selecting the best attribute to use at each tree node split. Overfitting is identified as a potential issue, and prepruning and postpruning techniques are described to address it.
The document discusses classification techniques for supervised learning problems. It describes classification as predicting categorical class labels based on a training set of labeled data. The classification process involves constructing a model from the training set and then using the model to classify new unlabeled data. Common classification techniques discussed include decision tree induction, Bayesian classification methods, and rule-based classification. Model evaluation and techniques for improving accuracy, such as ensemble methods, are also covered.
Data Mining Concepts and Techniques.pptRvishnupriya2
This document discusses classification techniques in data mining, including decision trees. It covers supervised vs. unsupervised learning, the classification process, decision tree induction using information gain and other measures, handling continuous attributes, overfitting, and tree pruning. Specific algorithms covered include ID3, C4.5, CART, and CHAID. The goal of classification and how decision trees are constructed from the training data is explained at a high level.
Data Mining Concepts and Techniques.pptRvishnupriya2
This document discusses classification techniques for data mining. It covers supervised and unsupervised learning methods. Specifically, it describes classification as a two-step process involving model construction from training data and then using the model to classify new data. Several classification algorithms are covered, including decision tree induction, Bayes classification, and rule-based classification. Evaluation metrics like accuracy and techniques to improve classification like ensemble methods are also summarized.
Jiawei Han, Micheline Kamber and Jian Pei
Data Mining: Concepts and Techniques, 3rd ed.
The Morgan Kaufmann Series in Data Management Systems
Morgan Kaufmann Publishers, July 2011. ISBN 978-0123814791
Machine learning is a branch of artificial intelligence (AI) and computer science which focuses on the use of data and algorithms to imitate the way that humans learn, gradually improving its accuracy.
IBM has a rich history with machine learning. One of its own, Arthur Samuel, is credited for coining the term, “machine learning” with his research (link resides outside ibm.com) around the game of checkers. Robert Nealey, the self-proclaimed checkers master, played the game on an IBM 7094 computer in 1962, and he lost to the computer. Compared to what can be done today, this feat seems trivial, but it’s considered a major milestone in the field of artificial intelligence.
Over the last couple of decades, the technological advances in storage and processing power have enabled some innovative products based on machine learning, such as Netflix’s recommendation engine and self-driving cars.
Machine learning is an important component of the growing field of data science. Through the use of statistical methods, algorithms are trained to make classifications or predictions, and to uncover key insights in data mining projects. These insights subsequently drive decision making within applications and businesses, ideally impacting key growth metrics. As big data continues to expand and grow, the market demand for data scientists will increase. They will be required to help identify the most relevant business questions and the data to answer them.
Machine learning algorithms are typically created using frameworks that accelerate solution development, such as TensorFlow and PyTorch.
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Machine Learning vs. Deep Learning vs. Neural Networks
Since deep learning and machine learning tend to be used interchangeably, it’s worth noting the nuances between the two. Machine learning, deep learning, and neural networks are all sub-fields of artificial intelligence. However, neural networks is actually a sub-field of machine learning, and deep learning is a sub-field of neural networks.
The way in which deep learning and machine learning differ is in how each algorithm learns. "Deep" machine learning can use labeled datasets, also known as supervised learning, to inform its algorithm, but it doesn’t necessarily require a labeled dataset. Deep learning can ingest unstructured data in its raw form (e.g., text or images), and it can automatically determine the set of features which distinguish different categories of data from one another. This eliminates some of the human intervention required and enables the use of larger data sets. You can think of deep learning as "scalable machine learning" as Lex Fridman notes in this MIT lecture (link resides outside ibm.com).
Classical, or "non-deep", machine learning is more dependent on human intervention to learn. Human experts determine the set of features to understand the differences between data inputs,
This chapter discusses classification techniques for data mining. It covers basic concepts of supervised learning and classification, including decision tree induction using information gain, gain ratio and gini index for attribute selection. It also discusses overfitting, tree pruning, and scaling classification to large databases using techniques like building attribute-value-class lists. The chapter provides examples and comparisons of different attribute selection measures and approaches to improve accuracy.
This document summarizes key concepts from Chapter 8 of the textbook "Data Mining: Concepts and Techniques". It discusses classification, which predicts categorical class labels, as a supervised learning technique. It covers decision trees for classification, which select attributes to split data recursively based on measures like information gain. It also discusses evaluating and improving classification models to avoid overfitting, and scaling classification to large databases.
This document summarizes key concepts from Chapter 8 of the textbook "Data Mining: Concepts and Techniques". It discusses classification, which predicts categorical class labels. The two main processes are model construction using a training set, and then using the model to classify new data. Decision trees, Naive Bayes, and rule-based classification algorithms are covered. Metrics for evaluating models like accuracy and techniques for improving accuracy like ensemble methods are also summarized.
This document summarizes key concepts from Chapter 8 of the textbook "Data Mining: Concepts and Techniques". It discusses classification, which predicts categorical class labels, as a supervised learning method. The two main steps of classification are model construction using a training set, and then using the model to classify new data. Decision trees are presented as a popular classification technique that uses measures like information gain or Gini index to build tree models that partition data into purer class subsets. The chapter covers decision tree algorithms, attribute selection, overfitting, and scaling classification to large datasets.
classification in data mining and data warehousing.pdf321106410027
The document discusses various classification techniques in machine learning. It begins with an overview of classification and supervised vs. unsupervised learning. Classification aims to predict categorical class labels by constructing a predictive model from labeled training data. Decision tree induction is then covered as a basic classification algorithm that recursively partitions data based on attribute values until reaching single class leaf nodes. Bayes classification methods are also mentioned, which classify examples based on applying Bayes' theorem to calculate posterior probabilities.
This document provides an overview of classification techniques for machine learning. It defines classification as predicting categorical class labels based on a training set. Decision tree induction and Bayes classification methods are described as common classification approaches. Decision trees are constructed recursively to partition data based on attribute tests. Information gain, gain ratio, and Gini index are discussed as measures for selecting the best attributes to test at each node. The naïve Bayes classifier is introduced as a simplified Bayesian approach based on conditional independence assumptions between attributes.
This document discusses classification techniques for supervised learning. It begins with an overview of classification and describes the two-step classification process of model construction using a training set and then applying the model to classify new data. It then covers specific classification algorithms like decision tree induction, Bayesian classification methods, and rule-based classification. It also discusses evaluating and selecting models as well as techniques for improving accuracy, such as ensemble methods.
2.1 Data Mining-classification Basic conceptsKrish_ver2
This document discusses classification and decision trees. It defines classification as predicting categorical class labels using a model constructed from a training set. Decision trees are a popular classification method that operate in a top-down recursive manner, splitting the data into purer subsets based on attribute values. The algorithm selects the optimal splitting attribute using an evaluation metric like information gain at each step until it reaches a leaf node containing only one class.
Descriptive and diagnostic analytics describe and analyze organizational data through measures like mean, median, standard deviation and charts/tables to identify patterns and insights. Predictive analytics use statistical techniques like regression and clustering to predict future outcomes and behaviors. Prescriptive analytics provide recommendations for decisions and actions based on optimization models. The document then focuses on classification techniques in predictive analytics, covering methods like decision trees, rules, Naive Bayes and nearest neighbor algorithms.
Model Preparation, Evaluation and Feature Engineering.pptxssuser29bd741
This document discusses model preparation, evaluation, and feature engineering for decision tree induction. It provides details on algorithms for decision tree induction, including attribute selection measures like information gain, gain ratio, and Gini index. The example decision tree is built using a training data set to predict whether someone buys a computer based on attributes like age, income, student status, and credit rating.
The document discusses various classification techniques in machine learning. It begins by distinguishing between supervised and unsupervised learning, with classification being a form of supervised learning where training data is labeled. It then describes classification as a two-step process of model construction using a training set, and model usage to classify new data. Several specific classification algorithms are covered, including decision trees, naive Bayes classification, and rule-based classification. The document also discusses evaluating classifier accuracy using methods like holdout validation, cross-validation, and bootstrap.
The document discusses various classification and prediction techniques used in machine learning, including decision trees, naive Bayes classification, and k-nearest neighbors. It provides examples of how these techniques work and compares supervised versus unsupervised learning approaches. The document also covers issues around preparing data and comparing different classification and prediction methods.
This chapter discusses data mining trends and research frontiers. It covers mining complex data types like sequences, time series, graphs and networks. It also discusses other data mining methodologies like statistical data mining and visual data mining. The chapter describes various data mining applications in domains like finance, retail, science and engineering. It also discusses data mining applications for intrusion detection, recommender systems and the role of data mining in society. Emerging trends in data mining like mining multi-relational data and streaming data are also presented.
This chapter discusses outlier analysis and various methods for outlier detection. It defines outliers as data objects that differ significantly from normal data. Several types of outliers are described, including global outliers that differ from all other data, contextual outliers that differ based on selected context attributes, and collective outliers where a group of objects collectively differ. Statistical, proximity-based, and clustering-based methods are some common approaches for outlier detection discussed in the chapter. Statistical approaches assume data follows a stochastic model, while proximity-based methods use distance measures and density-based methods to identify outliers. Clustering-based methods identify outliers as objects not belonging to large, dense clusters of normal data. Both supervised and unsupervised learning techniques can be applied to outlier detection.
1. Clustering high-dimensional data presents unique challenges as traditional distance measures become less meaningful and clusters may only exist in subspaces of the data. 2. Subspace clustering methods aim to find clusters that exist in subspaces of the feature space rather than the entire space. 3. Popular subspace clustering methods include subspace search approaches that examine various subspaces, bi-clustering methods, and dimensionality reduction techniques.
This document summarizes chapter 10 of the book "Data Mining: Concepts and Techniques" which discusses cluster analysis. The chapter covers basic concepts of cluster analysis including partitioning, hierarchical, density-based and grid-based methods. It describes popular partitioning algorithms like k-means and k-medoids, and notes that k-means can be sensitive to outliers while k-medoids uses medioids which are less sensitive to outliers. The chapter also discusses evaluating clustering quality and major considerations for cluster analysis.
This chapter discusses advanced classification methods, including Bayesian belief networks, classification using backpropagation neural networks, support vector machines (SVM), and lazy learners. It describes Bayesian belief networks as probabilistic graphical models that represent conditional dependencies between variables. Backpropagation neural networks are introduced as a way to perform nonlinear regression to approximate functions through adjusting weights in a multi-layer feedforward network. SVM is covered as a method that transforms data into a higher dimensional space to find an optimal separating hyperplane, using support vectors.
This chapter discusses advanced techniques for frequent pattern mining, including mining patterns in multi-level, multi-dimensional spaces by considering item hierarchies and multiple dimensions. It also covers constraint-based pattern mining where user-specified constraints are used to direct the mining process. Quantitative association rule mining is discussed, including techniques for discretizing numeric attributes. Mining rare and negative patterns is also addressed.
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3. 3
Chapter 8. Classification: Basic Concepts
Classification: Basic Concepts
Decision Tree Induction
Bayes Classification Methods
Rule-Based Classification
Model Evaluation and Selection
Techniques to Improve Classification Accuracy:
Ensemble Methods
Summary
4. 4
Supervised vs. Unsupervised Learning
Supervised learning (classification)
Supervision: The training data (observations,
measurements, etc.) are accompanied by labels indicating
the class of the observations
New data is classified based on the training set
Unsupervised learning (clustering)
The class labels of training data is unknown
Given a set of measurements, observations, etc. with the
aim of establishing the existence of classes or clusters in
the data
5. 5
Classification
predicts categorical class labels (discrete or nominal)
classifies data (constructs a model) based on the training
set and the values (class labels) in a classifying attribute
and uses it in classifying new data
Numeric Prediction
models continuous-valued functions, i.e., predicts
unknown or missing values
Typical applications
Credit/loan approval:
Medical diagnosis: if a tumor is cancerous or benign
Fraud detection: if a transaction is fraudulent
Web page categorization: which category it is
Prediction Problems: Classification vs.
Numeric Prediction
6. 6
Classification—A Two-Step Process
Model construction: describing a set of predetermined classes
Each tuple/sample is assumed to belong to a predefined class, as
determined by the class label attribute
The set of tuples used for model construction is training set
The model is represented as classification rules, decision trees, or
mathematical formulae
Model usage: for classifying future or unknown objects
Estimate accuracy of the model
The known label of test sample is compared with the classified
result from the model
Accuracy rate is the percentage of test set samples that are
correctly classified by the model
Test set is independent of training set (otherwise overfitting)
If the accuracy is acceptable, use the model to classify new data
Note: If the test set is used to select models, it is called validation (test) set
7. 7
Process (1): Model Construction
Training
Data
NAME RANK YEARS TENURED
Mike Assistant Prof 3 no
Mary Assistant Prof 7 yes
Bill Professor 2 yes
Jim Associate Prof 7 yes
Dave Assistant Prof 6 no
Anne Associate Prof 3 no
Classification
Algorithms
IF rank = ‘professor’
OR years > 6
THEN tenured = ‘yes’
Classifier
(Model)
8. 8
Process (2): Using the Model in Prediction
Classifier
Testing
Data
NAME RANK YEARS TENURED
Tom Assistant Prof 2 no
Merlisa Associate Prof 7 no
George Professor 5 yes
Joseph Assistant Prof 7 yes
Unseen Data
(Jeff, Professor, 4)
Tenured?
9. 9
Chapter 8. Classification: Basic Concepts
Classification: Basic Concepts
Decision Tree Induction
Bayes Classification Methods
Rule-Based Classification
Model Evaluation and Selection
Techniques to Improve Classification Accuracy:
Ensemble Methods
Summary
10. 10
Decision Tree Induction: An Example
age?
overcast
student? credit rating?
<=30 >40
no yes yes
yes
31..40
fairexcellentyesno
age income student credit_rating buys_computer
<=30 high no fair no
<=30 high no excellent no
31…40 high no fair yes
>40 medium no fair yes
>40 low yes fair yes
>40 low yes excellent no
31…40 low yes excellent yes
<=30 medium no fair no
<=30 low yes fair yes
>40 medium yes fair yes
<=30 medium yes excellent yes
31…40 medium no excellent yes
31…40 high yes fair yes
>40 medium no excellent no
Training data set: Buys_computer
The data set follows an example of
Quinlan’s ID3 (Playing Tennis)
Resulting tree:
11. 11
Algorithm for Decision Tree Induction
Basic algorithm (a greedy algorithm)
Tree is constructed in a top-down recursive divide-and-
conquer manner
At start, all the training examples are at the root
Attributes are categorical (if continuous-valued, they are
discretized in advance)
Examples are partitioned recursively based on selected
attributes
Test attributes are selected on the basis of a heuristic or
statistical measure (e.g., information gain)
Conditions for stopping partitioning
All samples for a given node belong to the same class
There are no remaining attributes for further partitioning –
majority voting is employed for classifying the leaf
There are no samples left
13. 13
Attribute Selection Measure:
Information Gain (ID3/C4.5)
Select the attribute with the highest information gain
Let pi be the probability that an arbitrary tuple in D belongs to
class Ci, estimated by |Ci, D|/|D|
Expected information (entropy) needed to classify a tuple in D:
Information needed (after using A to split D into v partitions) to
classify D:
Information gained by branching on attribute A
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14. 14
Attribute Selection: Information Gain
Class P: buys_computer = “yes”
Class N: buys_computer = “no”
means “age <=30” has 5 out of
14 samples, with 2 yes’es and 3
no’s. Hence
Similarly,
age pi ni I(pi, ni)
<=30 2 3 0.971
31…40 4 0 0
>40 3 2 0.971
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14
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studentGain
incomeGain
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age income student credit_rating buys_computer
<=30 high no fair no
<=30 high no excellent no
31…40 high no fair yes
>40 medium no fair yes
>40 low yes fair yes
>40 low yes excellent no
31…40 low yes excellent yes
<=30 medium no fair no
<=30 low yes fair yes
>40 medium yes fair yes
<=30 medium yes excellent yes
31…40 medium no excellent yes
31…40 high yes fair yes
>40 medium no excellent no
)3,2(
14
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15. 15
Computing Information-Gain for
Continuous-Valued Attributes
Let attribute A be a continuous-valued attribute
Must determine the best split point for A
Sort the value A in increasing order
Typically, the midpoint between each pair of adjacent values
is considered as a possible split point
(ai+ai+1)/2 is the midpoint between the values of ai and ai+1
The point with the minimum expected information
requirement for A is selected as the split-point for A
Split:
D1 is the set of tuples in D satisfying A ≤ split-point, and D2 is
the set of tuples in D satisfying A > split-point
16. 16
Gain Ratio for Attribute Selection (C4.5)
Information gain measure is biased towards attributes with a
large number of values
C4.5 (a successor of ID3) uses gain ratio to overcome the
problem (normalization to information gain)
GainRatio(A) = Gain(A)/SplitInfo(A)
Ex.
gain_ratio(income) = 0.029/1.557 = 0.019
The attribute with the maximum gain ratio is selected as the
splitting attribute
)
||
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||
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1 D
D
D
D
DSplitInfo
j
v
j
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17. 17
Gini Index (CART, IBM IntelligentMiner)
If a data set D contains examples from n classes, gini index,
gini(D) is defined as
where pj is the relative frequency of class j in D
If a data set D is split on A into two subsets D1 and D2, the gini
index gini(D) is defined as
Reduction in Impurity:
The attribute provides the smallest ginisplit(D) (or the largest
reduction in impurity) is chosen to split the node (need to
enumerate all the possible splitting points for each attribute)
n
j
p jDgini
1
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18. 18
Computation of Gini Index
Ex. D has 9 tuples in buys_computer = “yes” and 5 in “no”
Suppose the attribute income partitions D into 10 in D1: {low,
medium} and 4 in D2
Gini{low,high} is 0.458; Gini{medium,high} is 0.450. Thus, split on the
{low,medium} (and {high}) since it has the lowest Gini index
All attributes are assumed continuous-valued
May need other tools, e.g., clustering, to get the possible split
values
Can be modified for categorical attributes
459.0
14
5
14
9
1)(
22
Dgini
)(
14
4
)(
14
10
)( 21},{ DGiniDGiniDgini mediumlowincome
19. 19
Comparing Attribute Selection Measures
The three measures, in general, return good results but
Information gain:
biased towards multivalued attributes
Gain ratio:
tends to prefer unbalanced splits in which one partition is
much smaller than the others
Gini index:
biased to multivalued attributes
has difficulty when # of classes is large
tends to favor tests that result in equal-sized partitions
and purity in both partitions
20. 20
Other Attribute Selection Measures
CHAID: a popular decision tree algorithm, measure based on χ2 test for
independence
C-SEP: performs better than info. gain and gini index in certain cases
G-statistic: has a close approximation to χ2 distribution
MDL (Minimal Description Length) principle (i.e., the simplest solution is
preferred):
The best tree as the one that requires the fewest # of bits to both (1)
encode the tree, and (2) encode the exceptions to the tree
Multivariate splits (partition based on multiple variable combinations)
CART: finds multivariate splits based on a linear comb. of attrs.
Which attribute selection measure is the best?
Most give good results, none is significantly superior than others
21. 21
Overfitting and Tree Pruning
Overfitting: An induced tree may overfit the training data
Too many branches, some may reflect anomalies due to
noise or outliers
Poor accuracy for unseen samples
Two approaches to avoid overfitting
Prepruning: Halt tree construction early ̵ do not split a node
if this would result in the goodness measure falling below a
threshold
Difficult to choose an appropriate threshold
Postpruning: Remove branches from a “fully grown” tree—
get a sequence of progressively pruned trees
Use a set of data different from the training data to
decide which is the “best pruned tree”
22. 22
Enhancements to Basic Decision Tree Induction
Allow for continuous-valued attributes
Dynamically define new discrete-valued attributes that
partition the continuous attribute value into a discrete set of
intervals
Handle missing attribute values
Assign the most common value of the attribute
Assign probability to each of the possible values
Attribute construction
Create new attributes based on existing ones that are
sparsely represented
This reduces fragmentation, repetition, and replication
23. 23
Classification in Large Databases
Classification—a classical problem extensively studied by
statisticians and machine learning researchers
Scalability: Classifying data sets with millions of examples and
hundreds of attributes with reasonable speed
Why is decision tree induction popular?
relatively faster learning speed (than other classification
methods)
convertible to simple and easy to understand classification
rules
can use SQL queries for accessing databases
comparable classification accuracy with other methods
RainForest (VLDB’98 — Gehrke, Ramakrishnan & Ganti)
Builds an AVC-list (attribute, value, class label)
24. 24
Scalability Framework for RainForest
Separates the scalability aspects from the criteria that
determine the quality of the tree
Builds an AVC-list: AVC (Attribute, Value, Class_label)
AVC-set (of an attribute X )
Projection of training dataset onto the attribute X and
class label where counts of individual class label are
aggregated
AVC-group (of a node n )
Set of AVC-sets of all predictor attributes at the node n
25. 25
Rainforest: Training Set and Its AVC Sets
student Buy_Computer
yes no
yes 6 1
no 3 4
Age Buy_Computer
yes no
<=30 2 3
31..40 4 0
>40 3 2
Credit
rating
Buy_Computer
yes no
fair 6 2
excellent 3 3
age income studentcredit_ratingbuys_computer
<=30 high no fair no
<=30 high no excellent no
31…40 high no fair yes
>40 medium no fair yes
>40 low yes fair yes
>40 low yes excellent no
31…40 low yes excellent yes
<=30 medium no fair no
<=30 low yes fair yes
>40 medium yes fair yes
<=30 medium yes excellent yes
31…40 medium no excellent yes
31…40 high yes fair yes
>40 medium no excellent no
AVC-set on incomeAVC-set on Age
AVC-set on Student
Training Examples
income Buy_Computer
yes no
high 2 2
medium 4 2
low 3 1
AVC-set on
credit_rating
26. 26
BOAT (Bootstrapped Optimistic
Algorithm for Tree Construction)
Use a statistical technique called bootstrapping to create
several smaller samples (subsets), each fits in memory
Each subset is used to create a tree, resulting in several
trees
These trees are examined and used to construct a new
tree T’
It turns out that T’ is very close to the tree that would
be generated using the whole data set together
Adv: requires only two scans of DB, an incremental alg.
27. October 31, 2019 Data Mining: Concepts and Techniques 27
Presentation of Classification Results
28. October 31, 2019 Data Mining: Concepts and Techniques 28
Visualization of a Decision Tree in SGI/MineSet 3.0
29. Data Mining: Concepts and Techniques 29
Interactive Visual Mining by Perception-
Based Classification (PBC)
30. 30
Chapter 8. Classification: Basic Concepts
Classification: Basic Concepts
Decision Tree Induction
Bayes Classification Methods
Rule-Based Classification
Model Evaluation and Selection
Techniques to Improve Classification Accuracy:
Ensemble Methods
Summary
31. 31
Bayesian Classification: Why?
A statistical classifier: performs probabilistic prediction, i.e.,
predicts class membership probabilities
Foundation: Based on Bayes’ Theorem.
Performance: A simple Bayesian classifier, naïve Bayesian
classifier, has comparable performance with decision tree and
selected neural network classifiers
Incremental: Each training example can incrementally
increase/decrease the probability that a hypothesis is correct —
prior knowledge can be combined with observed data
Standard: Even when Bayesian methods are computationally
intractable, they can provide a standard of optimal decision
making against which other methods can be measured
32. 32
Bayes’ Theorem: Basics
Total probability Theorem:
Bayes’ Theorem:
Let X be a data sample (“evidence”): class label is unknown
Let H be a hypothesis that X belongs to class C
Classification is to determine P(H|X), (i.e., posteriori probability): the
probability that the hypothesis holds given the observed data sample X
P(H) (prior probability): the initial probability
E.g., X will buy computer, regardless of age, income, …
P(X): probability that sample data is observed
P(X|H) (likelihood): the probability of observing the sample X, given that
the hypothesis holds
E.g., Given that X will buy computer, the prob. that X is 31..40,
medium income
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33. 33
Prediction Based on Bayes’ Theorem
Given training data X, posteriori probability of a hypothesis H,
P(H|X), follows the Bayes’ theorem
Informally, this can be viewed as
posteriori = likelihood x prior/evidence
Predicts X belongs to Ci iff the probability P(Ci|X) is the highest
among all the P(Ck|X) for all the k classes
Practical difficulty: It requires initial knowledge of many
probabilities, involving significant computational cost
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34. 34
Classification Is to Derive the Maximum Posteriori
Let D be a training set of tuples and their associated class
labels, and each tuple is represented by an n-D attribute vector
X = (x1, x2, …, xn)
Suppose there are m classes C1, C2, …, Cm.
Classification is to derive the maximum posteriori, i.e., the
maximal P(Ci|X)
This can be derived from Bayes’ theorem
Since P(X) is constant for all classes, only
needs to be maximized
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35. 35
Naïve Bayes Classifier
A simplified assumption: attributes are conditionally
independent (i.e., no dependence relation between
attributes):
This greatly reduces the computation cost: Only counts the
class distribution
If Ak is categorical, P(xk|Ci) is the # of tuples in Ci having value xk
for Ak divided by |Ci, D| (# of tuples of Ci in D)
If Ak is continous-valued, P(xk|Ci) is usually computed based on
Gaussian distribution with a mean μ and standard deviation σ
and P(xk|Ci) is
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36. 36
Naïve Bayes Classifier: Training Dataset
Class:
C1:buys_computer = ‘yes’
C2:buys_computer = ‘no’
Data to be classified:
X = (age <=30,
Income = medium,
Student = yes
Credit_rating = Fair)
age income studentcredit_ratingbuys_compu
<=30 high no fair no
<=30 high no excellent no
31…40 high no fair yes
>40 medium no fair yes
>40 low yes fair yes
>40 low yes excellent no
31…40 low yes excellent yes
<=30 medium no fair no
<=30 low yes fair yes
>40 medium yes fair yes
<=30 medium yes excellent yes
31…40 medium no excellent yes
31…40 high yes fair yes
>40 medium no excellent no
37. 37
Naïve Bayes Classifier: An Example
P(Ci): P(buys_computer = “yes”) = 9/14 = 0.643
P(buys_computer = “no”) = 5/14= 0.357
Compute P(X|Ci) for each class
P(age = “<=30” | buys_computer = “yes”) = 2/9 = 0.222
P(age = “<= 30” | buys_computer = “no”) = 3/5 = 0.6
P(income = “medium” | buys_computer = “yes”) = 4/9 = 0.444
P(income = “medium” | buys_computer = “no”) = 2/5 = 0.4
P(student = “yes” | buys_computer = “yes) = 6/9 = 0.667
P(student = “yes” | buys_computer = “no”) = 1/5 = 0.2
P(credit_rating = “fair” | buys_computer = “yes”) = 6/9 = 0.667
P(credit_rating = “fair” | buys_computer = “no”) = 2/5 = 0.4
X = (age <= 30 , income = medium, student = yes, credit_rating = fair)
P(X|Ci) : P(X|buys_computer = “yes”) = 0.222 x 0.444 x 0.667 x 0.667 = 0.044
P(X|buys_computer = “no”) = 0.6 x 0.4 x 0.2 x 0.4 = 0.019
P(X|Ci)*P(Ci) : P(X|buys_computer = “yes”) * P(buys_computer = “yes”) = 0.028
P(X|buys_computer = “no”) * P(buys_computer = “no”) = 0.007
Therefore, X belongs to class (“buys_computer = yes”)
age income studentcredit_ratingbuys_comp
<=30 high no fair no
<=30 high no excellent no
31…40 high no fair yes
>40 medium no fair yes
>40 low yes fair yes
>40 low yes excellent no
31…40 low yes excellent yes
<=30 medium no fair no
<=30 low yes fair yes
>40 medium yes fair yes
<=30 medium yes excellent yes
31…40 medium no excellent yes
31…40 high yes fair yes
>40 medium no excellent no
38. 38
Avoiding the Zero-Probability Problem
Naïve Bayesian prediction requires each conditional prob. be
non-zero. Otherwise, the predicted prob. will be zero
Ex. Suppose a dataset with 1000 tuples, income=low (0),
income= medium (990), and income = high (10)
Use Laplacian correction (or Laplacian estimator)
Adding 1 to each case
Prob(income = low) = 1/1003
Prob(income = medium) = 991/1003
Prob(income = high) = 11/1003
The “corrected” prob. estimates are close to their
“uncorrected” counterparts
n
k
CixkPCiXP
1
)|()|(
39. 39
Naïve Bayes Classifier: Comments
Advantages
Easy to implement
Good results obtained in most of the cases
Disadvantages
Assumption: class conditional independence, therefore loss
of accuracy
Practically, dependencies exist among variables
E.g., hospitals: patients: Profile: age, family history, etc.
Symptoms: fever, cough etc., Disease: lung cancer,
diabetes, etc.
Dependencies among these cannot be modeled by Naïve
Bayes Classifier
How to deal with these dependencies? Bayesian Belief Networks
(Chapter 9)
40. 40
Chapter 8. Classification: Basic Concepts
Classification: Basic Concepts
Decision Tree Induction
Bayes Classification Methods
Rule-Based Classification
Model Evaluation and Selection
Techniques to Improve Classification Accuracy:
Ensemble Methods
Summary
41. 41
Using IF-THEN Rules for Classification
Represent the knowledge in the form of IF-THEN rules
R: IF age = youth AND student = yes THEN buys_computer = yes
Rule antecedent/precondition vs. rule consequent
Assessment of a rule: coverage and accuracy
ncovers = # of tuples covered by R
ncorrect = # of tuples correctly classified by R
coverage(R) = ncovers /|D| /* D: training data set */
accuracy(R) = ncorrect / ncovers
If more than one rule are triggered, need conflict resolution
Size ordering: assign the highest priority to the triggering rules that has
the “toughest” requirement (i.e., with the most attribute tests)
Class-based ordering: decreasing order of prevalence or misclassification
cost per class
Rule-based ordering (decision list): rules are organized into one long
priority list, according to some measure of rule quality or by experts
42. 42
age?
student? credit rating?
<=30 >40
no yes yes
yes
31..40
fairexcellentyesno
Example: Rule extraction from our buys_computer decision-tree
IF age = young AND student = no THEN buys_computer = no
IF age = young AND student = yes THEN buys_computer = yes
IF age = mid-age THEN buys_computer = yes
IF age = old AND credit_rating = excellent THEN buys_computer = no
IF age = old AND credit_rating = fair THEN buys_computer = yes
Rule Extraction from a Decision Tree
Rules are easier to understand than large
trees
One rule is created for each path from the
root to a leaf
Each attribute-value pair along a path forms a
conjunction: the leaf holds the class
prediction
Rules are mutually exclusive and exhaustive
43. 43
Rule Induction: Sequential Covering Method
Sequential covering algorithm: Extracts rules directly from training
data
Typical sequential covering algorithms: FOIL, AQ, CN2, RIPPER
Rules are learned sequentially, each for a given class Ci will cover
many tuples of Ci but none (or few) of the tuples of other classes
Steps:
Rules are learned one at a time
Each time a rule is learned, the tuples covered by the rules are
removed
Repeat the process on the remaining tuples until termination
condition, e.g., when no more training examples or when the
quality of a rule returned is below a user-specified threshold
Comp. w. decision-tree induction: learning a set of rules
simultaneously
44. 44
Sequential Covering Algorithm
while (enough target tuples left)
generate a rule
remove positive target tuples satisfying this rule
Examples covered
by Rule 3
Examples covered
by Rule 2Examples covered
by Rule 1
Positive
examples
45. 45
Rule Generation
To generate a rule
while(true)
find the best predicate p
if foil-gain(p) > threshold then add p to current rule
else break
Positive
examples
Negative
examples
A3=1
A3=1&&A1=2
A3=1&&A1=2
&&A8=5
46. 46
How to Learn-One-Rule?
Start with the most general rule possible: condition = empty
Adding new attributes by adopting a greedy depth-first strategy
Picks the one that most improves the rule quality
Rule-Quality measures: consider both coverage and accuracy
Foil-gain (in FOIL & RIPPER): assesses info_gain by extending
condition
favors rules that have high accuracy and cover many positive tuples
Rule pruning based on an independent set of test tuples
Pos/neg are # of positive/negative tuples covered by R.
If FOIL_Prune is higher for the pruned version of R, prune R
)log
''
'
(log'_ 22
negpos
pos
negpos
pos
posGainFOIL
negpos
negpos
RPruneFOIL
)(_
47. 47
Chapter 8. Classification: Basic Concepts
Classification: Basic Concepts
Decision Tree Induction
Bayes Classification Methods
Rule-Based Classification
Model Evaluation and Selection
Techniques to Improve Classification Accuracy:
Ensemble Methods
Summary
48. Model Evaluation and Selection
Evaluation metrics: How can we measure accuracy? Other
metrics to consider?
Use validation test set of class-labeled tuples instead of
training set when assessing accuracy
Methods for estimating a classifier’s accuracy:
Holdout method, random subsampling
Cross-validation
Bootstrap
Comparing classifiers:
Confidence intervals
Cost-benefit analysis and ROC Curves
48
49. Classifier Evaluation Metrics: Confusion
Matrix
Actual classPredicted
class
buy_computer
= yes
buy_computer
= no
Total
buy_computer = yes 6954 46 7000
buy_computer = no 412 2588 3000
Total 7366 2634 10000
Given m classes, an entry, CMi,j in a confusion matrix indicates
# of tuples in class i that were labeled by the classifier as class j
May have extra rows/columns to provide totals
Confusion Matrix:
Actual classPredicted class C1 ¬ C1
C1 True Positives (TP) False Negatives (FN)
¬ C1 False Positives (FP) True Negatives (TN)
Example of Confusion Matrix:
49
50. Classifier Evaluation Metrics: Accuracy,
Error Rate, Sensitivity and Specificity
Classifier Accuracy, or
recognition rate: percentage of
test set tuples that are correctly
classified
Accuracy = (TP + TN)/All
Error rate: 1 – accuracy, or
Error rate = (FP + FN)/All
Class Imbalance Problem:
One class may be rare, e.g.
fraud, or HIV-positive
Significant majority of the
negative class and minority of
the positive class
Sensitivity: True Positive
recognition rate
Sensitivity = TP/P
Specificity: True Negative
recognition rate
Specificity = TN/N
AP C ¬C
C TP FN P
¬C FP TN N
P’ N’ All
50
51. Classifier Evaluation Metrics:
Precision and Recall, and F-measures
Precision: exactness – what % of tuples that the classifier
labeled as positive are actually positive
Recall: completeness – what % of positive tuples did the
classifier label as positive?
Perfect score is 1.0
Inverse relationship between precision & recall
F measure (F1 or F-score): harmonic mean of precision and
recall,
Fß: weighted measure of precision and recall
assigns ß times as much weight to recall as to precision
51
52. Classifier Evaluation Metrics: Example
52
Precision = 90/230 = 39.13% Recall = 90/300 = 30.00%
Actual ClassPredicted class cancer = yes cancer = no Total Recognition(%)
cancer = yes 90 210 300 30.00 (sensitivity
cancer = no 140 9560 9700 98.56 (specificity)
Total 230 9770 10000 96.40 (accuracy)
53. Evaluating Classifier Accuracy:
Holdout & Cross-Validation Methods
Holdout method
Given data is randomly partitioned into two independent sets
Training set (e.g., 2/3) for model construction
Test set (e.g., 1/3) for accuracy estimation
Random sampling: a variation of holdout
Repeat holdout k times, accuracy = avg. of the accuracies
obtained
Cross-validation (k-fold, where k = 10 is most popular)
Randomly partition the data into k mutually exclusive subsets,
each approximately equal size
At i-th iteration, use Di as test set and others as training set
Leave-one-out: k folds where k = # of tuples, for small sized
data
*Stratified cross-validation*: folds are stratified so that class
dist. in each fold is approx. the same as that in the initial data
53
54. Evaluating Classifier Accuracy: Bootstrap
Bootstrap
Works well with small data sets
Samples the given training tuples uniformly with replacement
i.e., each time a tuple is selected, it is equally likely to be selected
again and re-added to the training set
Several bootstrap methods, and a common one is .632 boostrap
A data set with d tuples is sampled d times, with replacement, resulting in
a training set of d samples. The data tuples that did not make it into the
training set end up forming the test set. About 63.2% of the original data
end up in the bootstrap, and the remaining 36.8% form the test set (since
(1 – 1/d)d ≈ e-1 = 0.368)
Repeat the sampling procedure k times, overall accuracy of the model:
54
55. Estimating Confidence Intervals:
Classifier Models M1 vs. M2
Suppose we have 2 classifiers, M1 and M2, which one is better?
Use 10-fold cross-validation to obtain and
These mean error rates are just estimates of error on the true
population of future data cases
What if the difference between the 2 error rates is just
attributed to chance?
Use a test of statistical significance
Obtain confidence limits for our error estimates
55
56. Estimating Confidence Intervals:
Null Hypothesis
Perform 10-fold cross-validation
Assume samples follow a t distribution with k–1 degrees of
freedom (here, k=10)
Use t-test (or Student’s t-test)
Null Hypothesis: M1 & M2 are the same
If we can reject null hypothesis, then
we conclude that the difference between M1 & M2 is
statistically significant
Chose model with lower error rate
56
57. Estimating Confidence Intervals: t-test
If only 1 test set available: pairwise comparison
For ith round of 10-fold cross-validation, the same cross
partitioning is used to obtain err(M1)i and err(M2)i
Average over 10 rounds to get
t-test computes t-statistic with k-1 degrees of
freedom:
If two test sets available: use non-paired t-test
where
and
where
where k1 & k2 are # of cross-validation samples used for M1 & M2, resp.
57
58. Estimating Confidence Intervals:
Table for t-distribution
Symmetric
Significance level,
e.g., sig = 0.05 or
5% means M1 & M2
are significantly
different for 95% of
population
Confidence limit, z
= sig/2
58
59. Estimating Confidence Intervals:
Statistical Significance
Are M1 & M2 significantly different?
Compute t. Select significance level (e.g. sig = 5%)
Consult table for t-distribution: Find t value corresponding
to k-1 degrees of freedom (here, 9)
t-distribution is symmetric: typically upper % points of
distribution shown → look up value for confidence limit
z=sig/2 (here, 0.025)
If t > z or t < -z, then t value lies in rejection region:
Reject null hypothesis that mean error rates of M1 & M2
are same
Conclude: statistically significant difference between M1
& M2
Otherwise, conclude that any difference is chance
59
60. Model Selection: ROC Curves
ROC (Receiver Operating
Characteristics) curves: for visual
comparison of classification models
Originated from signal detection theory
Shows the trade-off between the true
positive rate and the false positive rate
The area under the ROC curve is a
measure of the accuracy of the model
Rank the test tuples in decreasing
order: the one that is most likely to
belong to the positive class appears at
the top of the list
The closer to the diagonal line (i.e., the
closer the area is to 0.5), the less
accurate is the model
Vertical axis
represents the true
positive rate
Horizontal axis rep.
the false positive rate
The plot also shows a
diagonal line
A model with perfect
accuracy will have an
area of 1.0
60
61. Issues Affecting Model Selection
Accuracy
classifier accuracy: predicting class label
Speed
time to construct the model (training time)
time to use the model (classification/prediction time)
Robustness: handling noise and missing values
Scalability: efficiency in disk-resident databases
Interpretability
understanding and insight provided by the model
Other measures, e.g., goodness of rules, such as decision tree
size or compactness of classification rules
61
62. 62
Chapter 8. Classification: Basic Concepts
Classification: Basic Concepts
Decision Tree Induction
Bayes Classification Methods
Rule-Based Classification
Model Evaluation and Selection
Techniques to Improve Classification Accuracy:
Ensemble Methods
Summary
63. Ensemble Methods: Increasing the Accuracy
Ensemble methods
Use a combination of models to increase accuracy
Combine a series of k learned models, M1, M2, …, Mk, with
the aim of creating an improved model M*
Popular ensemble methods
Bagging: averaging the prediction over a collection of
classifiers
Boosting: weighted vote with a collection of classifiers
Ensemble: combining a set of heterogeneous classifiers
63
64. Bagging: Boostrap Aggregation
Analogy: Diagnosis based on multiple doctors’ majority vote
Training
Given a set D of d tuples, at each iteration i, a training set Di of d tuples
is sampled with replacement from D (i.e., bootstrap)
A classifier model Mi is learned for each training set Di
Classification: classify an unknown sample X
Each classifier Mi returns its class prediction
The bagged classifier M* counts the votes and assigns the class with the
most votes to X
Prediction: can be applied to the prediction of continuous values by taking
the average value of each prediction for a given test tuple
Accuracy
Often significantly better than a single classifier derived from D
For noise data: not considerably worse, more robust
Proved improved accuracy in prediction
64
65. Boosting
Analogy: Consult several doctors, based on a combination of
weighted diagnoses—weight assigned based on the previous
diagnosis accuracy
How boosting works?
Weights are assigned to each training tuple
A series of k classifiers is iteratively learned
After a classifier Mi is learned, the weights are updated to
allow the subsequent classifier, Mi+1, to pay more attention to
the training tuples that were misclassified by Mi
The final M* combines the votes of each individual classifier,
where the weight of each classifier's vote is a function of its
accuracy
Boosting algorithm can be extended for numeric prediction
Comparing with bagging: Boosting tends to have greater accuracy,
but it also risks overfitting the model to misclassified data 65
66. 66
Adaboost (Freund and Schapire, 1997)
Given a set of d class-labeled tuples, (X1, y1), …, (Xd, yd)
Initially, all the weights of tuples are set the same (1/d)
Generate k classifiers in k rounds. At round i,
Tuples from D are sampled (with replacement) to form a training set
Di of the same size
Each tuple’s chance of being selected is based on its weight
A classification model Mi is derived from Di
Its error rate is calculated using Di as a test set
If a tuple is misclassified, its weight is increased, o.w. it is decreased
Error rate: err(Xj) is the misclassification error of tuple Xj. Classifier Mi
error rate is the sum of the weights of the misclassified tuples:
The weight of classifier Mi’s vote is
)(
)(1
log
i
i
Merror
Merror
d
j
ji errwMerror )()( jX
67. Random Forest (Breiman 2001)
Random Forest:
Each classifier in the ensemble is a decision tree classifier and is
generated using a random selection of attributes at each node to
determine the split
During classification, each tree votes and the most popular class is
returned
Two Methods to construct Random Forest:
Forest-RI (random input selection): Randomly select, at each node, F
attributes as candidates for the split at the node. The CART methodology
is used to grow the trees to maximum size
Forest-RC (random linear combinations): Creates new attributes (or
features) that are a linear combination of the existing attributes
(reduces the correlation between individual classifiers)
Comparable in accuracy to Adaboost, but more robust to errors and outliers
Insensitive to the number of attributes selected for consideration at each
split, and faster than bagging or boosting
67
68. Classification of Class-Imbalanced Data Sets
Class-imbalance problem: Rare positive example but numerous
negative ones, e.g., medical diagnosis, fraud, oil-spill, fault, etc.
Traditional methods assume a balanced distribution of classes
and equal error costs: not suitable for class-imbalanced data
Typical methods for imbalance data in 2-class classification:
Oversampling: re-sampling of data from positive class
Under-sampling: randomly eliminate tuples from negative
class
Threshold-moving: moves the decision threshold, t, so that
the rare class tuples are easier to classify, and hence, less
chance of costly false negative errors
Ensemble techniques: Ensemble multiple classifiers
introduced above
Still difficult for class imbalance problem on multiclass tasks
68
69. 69
Chapter 8. Classification: Basic Concepts
Classification: Basic Concepts
Decision Tree Induction
Bayes Classification Methods
Rule-Based Classification
Model Evaluation and Selection
Techniques to Improve Classification Accuracy:
Ensemble Methods
Summary
70. Summary (I)
Classification is a form of data analysis that extracts models
describing important data classes.
Effective and scalable methods have been developed for decision
tree induction, Naive Bayesian classification, rule-based
classification, and many other classification methods.
Evaluation metrics include: accuracy, sensitivity, specificity,
precision, recall, F measure, and Fß measure.
Stratified k-fold cross-validation is recommended for accuracy
estimation. Bagging and boosting can be used to increase overall
accuracy by learning and combining a series of individual models.
70
71. Summary (II)
Significance tests and ROC curves are useful for model selection.
There have been numerous comparisons of the different
classification methods; the matter remains a research topic
No single method has been found to be superior over all others
for all data sets
Issues such as accuracy, training time, robustness, scalability,
and interpretability must be considered and can involve trade-
offs, further complicating the quest for an overall superior
method
71
72. References (1)
C. Apte and S. Weiss. Data mining with decision trees and decision rules. Future
Generation Computer Systems, 13, 1997
C. M. Bishop, Neural Networks for Pattern Recognition. Oxford University Press,
1995
L. Breiman, J. Friedman, R. Olshen, and C. Stone. Classification and Regression Trees.
Wadsworth International Group, 1984
C. J. C. Burges. A Tutorial on Support Vector Machines for Pattern Recognition. Data
Mining and Knowledge Discovery, 2(2): 121-168, 1998
P. K. Chan and S. J. Stolfo. Learning arbiter and combiner trees from partitioned data
for scaling machine learning. KDD'95
H. Cheng, X. Yan, J. Han, and C.-W. Hsu, Discriminative Frequent Pattern Analysis for
Effective Classification, ICDE'07
H. Cheng, X. Yan, J. Han, and P. S. Yu, Direct Discriminative Pattern Mining for
Effective Classification, ICDE'08
W. Cohen. Fast effective rule induction. ICML'95
G. Cong, K.-L. Tan, A. K. H. Tung, and X. Xu. Mining top-k covering rule groups for
gene expression data. SIGMOD'05
72
73. References (2)
A. J. Dobson. An Introduction to Generalized Linear Models. Chapman & Hall, 1990.
G. Dong and J. Li. Efficient mining of emerging patterns: Discovering trends and
differences. KDD'99.
R. O. Duda, P. E. Hart, and D. G. Stork. Pattern Classification, 2ed. John Wiley, 2001
U. M. Fayyad. Branching on attribute values in decision tree generation. AAAI’94.
Y. Freund and R. E. Schapire. A decision-theoretic generalization of on-line learning and
an application to boosting. J. Computer and System Sciences, 1997.
J. Gehrke, R. Ramakrishnan, and V. Ganti. Rainforest: A framework for fast decision tree
construction of large datasets. VLDB’98.
J. Gehrke, V. Gant, R. Ramakrishnan, and W.-Y. Loh, BOAT -- Optimistic Decision Tree
Construction. SIGMOD'99.
T. Hastie, R. Tibshirani, and J. Friedman. The Elements of Statistical Learning: Data
Mining, Inference, and Prediction. Springer-Verlag, 2001.
D. Heckerman, D. Geiger, and D. M. Chickering. Learning Bayesian networks: The
combination of knowledge and statistical data. Machine Learning, 1995.
W. Li, J. Han, and J. Pei, CMAR: Accurate and Efficient Classification Based on Multiple
Class-Association Rules, ICDM'01.
73
74. References (3)
T.-S. Lim, W.-Y. Loh, and Y.-S. Shih. A comparison of prediction accuracy, complexity,
and training time of thirty-three old and new classification algorithms. Machine
Learning, 2000.
J. Magidson. The Chaid approach to segmentation modeling: Chi-squared
automatic interaction detection. In R. P. Bagozzi, editor, Advanced Methods of
Marketing Research, Blackwell Business, 1994.
M. Mehta, R. Agrawal, and J. Rissanen. SLIQ : A fast scalable classifier for data
mining. EDBT'96.
T. M. Mitchell. Machine Learning. McGraw Hill, 1997.
S. K. Murthy, Automatic Construction of Decision Trees from Data: A Multi-
Disciplinary Survey, Data Mining and Knowledge Discovery 2(4): 345-389, 1998
J. R. Quinlan. Induction of decision trees. Machine Learning, 1:81-106, 1986.
J. R. Quinlan and R. M. Cameron-Jones. FOIL: A midterm report. ECML’93.
J. R. Quinlan. C4.5: Programs for Machine Learning. Morgan Kaufmann, 1993.
J. R. Quinlan. Bagging, boosting, and c4.5. AAAI'96.
74
75. References (4)
R. Rastogi and K. Shim. Public: A decision tree classifier that integrates building and
pruning. VLDB’98.
J. Shafer, R. Agrawal, and M. Mehta. SPRINT : A scalable parallel classifier for data
mining. VLDB’96.
J. W. Shavlik and T. G. Dietterich. Readings in Machine Learning. Morgan Kaufmann,
1990.
P. Tan, M. Steinbach, and V. Kumar. Introduction to Data Mining. Addison Wesley,
2005.
S. M. Weiss and C. A. Kulikowski. Computer Systems that Learn: Classification and
Prediction Methods from Statistics, Neural Nets, Machine Learning, and Expert
Systems. Morgan Kaufman, 1991.
S. M. Weiss and N. Indurkhya. Predictive Data Mining. Morgan Kaufmann, 1997.
I. H. Witten and E. Frank. Data Mining: Practical Machine Learning Tools and
Techniques, 2ed. Morgan Kaufmann, 2005.
X. Yin and J. Han. CPAR: Classification based on predictive association rules. SDM'03
H. Yu, J. Yang, and J. Han. Classifying large data sets using SVM with hierarchical
clusters. KDD'03.
75
76.
77. CS412 Midterm Exam Statistics
Opinion Question Answering:
Like the style: 70.83%, dislike: 29.16%
Exam is hard: 55.75%, easy: 0.6%, just right: 43.63%
Time: plenty:3.03%, enough: 36.96%, not: 60%
Score distribution: # of students (Total: 180)
>=90: 24
80-89: 54
70-79: 46
Final grading are based on overall score accumulation
and relative class distributions
77
60-69: 37
50-59: 15
40-49: 2
<40: 2
78. 78
Issues: Evaluating Classification Methods
Accuracy
classifier accuracy: predicting class label
predictor accuracy: guessing value of predicted attributes
Speed
time to construct the model (training time)
time to use the model (classification/prediction time)
Robustness: handling noise and missing values
Scalability: efficiency in disk-resident databases
Interpretability
understanding and insight provided by the model
Other measures, e.g., goodness of rules, such as decision tree
size or compactness of classification rules
79. 79
Predictor Error Measures
Measure predictor accuracy: measure how far off the predicted value is from
the actual known value
Loss function: measures the error betw. yi and the predicted value yi’
Absolute error: | yi – yi’|
Squared error: (yi – yi’)2
Test error (generalization error): the average loss over the test set
Mean absolute error: Mean squared error:
Relative absolute error: Relative squared error:
The mean squared-error exaggerates the presence of outliers
Popularly use (square) root mean-square error, similarly, root relative
squared error
d
yy
d
i
ii
1
|'|
d
yy
d
i
ii
1
2
)'(
d
i
i
d
i
ii
yy
yy
1
1
||
|'|
d
i
i
d
i
ii
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2
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80. 80
Scalable Decision Tree Induction Methods
SLIQ (EDBT’96 — Mehta et al.)
Builds an index for each attribute and only class list and the
current attribute list reside in memory
SPRINT (VLDB’96 — J. Shafer et al.)
Constructs an attribute list data structure
PUBLIC (VLDB’98 — Rastogi & Shim)
Integrates tree splitting and tree pruning: stop growing the
tree earlier
RainForest (VLDB’98 — Gehrke, Ramakrishnan & Ganti)
Builds an AVC-list (attribute, value, class label)
BOAT (PODS’99 — Gehrke, Ganti, Ramakrishnan & Loh)
Uses bootstrapping to create several small samples
81. 81
Data Cube-Based Decision-Tree Induction
Integration of generalization with decision-tree induction
(Kamber et al.’97)
Classification at primitive concept levels
E.g., precise temperature, humidity, outlook, etc.
Low-level concepts, scattered classes, bushy classification-
trees
Semantic interpretation problems
Cube-based multi-level classification
Relevance analysis at multi-levels
Information-gain analysis with dimension + level