4. Decision Tree:
A decision tree is a graphical representation of possible solutions to a
decision based on certain conditions.
It's called a decision tree because it starts with a single box (or root),
which then branches off into a number of solutions, just like a tree.
Decision trees provide an effective method of Decision Making.
5. Decision Tree:
A decision tree consists of 3 types of nodes
1. Decision nodes - commonly represented
by squares
2. Chance nodes - represented by circles
3. End nodes - represented by triangles
A decision tree consists of 2 types of
branches :
1. Decision branches
2. Event branches
7. Algorithm
Input:
D // Training data
Output:
T //Decision tree
DT Build algorithm
// Simplistic algorithm to illustrate naive approach to building DT
8. Types of Decision Trees:
Types of decision tree is based on the type of target variable we
have. It can be of two types:
Categorical Variable Decision Tree
Continuous Variable Decision Tree
9. Categorical Variable Decision Tree:
Categorical Variable Decision Tree:
Decision Tree which has categorical
target variable then it called as
categorical variable decision tree.
E.g.:- In scenario, where the target
variable was “Student will distributed
in gender and height” i.e. YES or NO.
10. Continuous Variable Decision Tree:
Continuous Variable Decision Tree:
Decision Tree has continuous target variable then it is called as
Continuous Variable Decision Tree.
E.g.:-
A worker thinking about his salary and take decision. Is he accept
new job offer(yes/ no). In this case, we are predicting values for
continuous variable.
12. Assumptions while creating Decision Tree:
Some of the assumptions we make while using Decision tree:
At the beginning, the whole training set is considered as the root.
Feature values are preferred to be categorical. If the values are
continuous then they are discretized prior to building the model.
Records are distributed recursively on the basis of attribute values.
Order to placing attributes as root or internal node of the tree is done
by using some statistical approach.
16. Advantages:
Decision Trees are easy to explain. It results in a set of rules.
It follows the same approach as humans generally follow while
making decisions.
Interpretation of a complex Decision Tree model can be simplified by
its visualizations. Even a naive person can understand logic.
The Number of hyper-parameters to be tuned is almost null.
It can be combined with other decision techniques.
17. Limitation:
There is a high probability of overfitting in Decision Tree.
Generally, it gives low prediction accuracy for a dataset as compared
to other machine learning algorithms.
Information gain in a decision tree with categorical variables gives a
biased response for attributes with greater no. of categories.
Calculations can become complex when there are many class labels.
18. Application of decision Tree:
Decision tree has been used to develop models for prediction and
classification in different domains some of which are:
Business management
Customer relationship management
Fraudulent statement detection
Engineering
Energy consumption
Fault diagnosis
Healthcare management
Agriculture
19. Applications in Real Life
Selecting a flight to travel
Choosing a best friend
Handling late night cravings
20. Applications in Business
Alternatives: Decision tree helps organizations to view the
alternatives way that can happen.
Events: Possible result may have two events.
Outcomes: Possible result from the decision tree.
21. References:
Kamiński, B.; Jakubczyk, M.; Szufel, P. (2017). "A framework for
sensitivity analysis of decision trees“
Quinlan, J. R. (1987). "Simplifying decision trees". International
Journal of Man-Machine Studies.
Venky Rao(2013 ).Journal “Introduction to Classification & Regression
Trees (CART).
Utgoff, P. E. (1989). “Incremental induction of decision trees”.
Machine learning.