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R Programming: Variables & Data Types

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In this tutorial, we learn to create variables in R. Followed by that, we explore the different data types including numeric, integer, character, logical and date/time.

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R Programming: Variables & Data Types

  1. 1. www.r-squared.in/git-hub R2 Academy R Programming Variables & Data Types
  2. 2. R2 AcademyCourse Material Slide 2 All the material related to this course are available at our website Slides can be viewed at SlideShare Scripts can be downloaded from GitHub Videos can be viewed on our Youtube Channel
  3. 3. R2 AcademyObjectives Slide 3 Variables ➢ What is a variable? ➢ How to create a variable? ➢ How to assign value? ➢ Understand rules for naming variables Data Types ➢ Numeric ➢ Integer ➢ Character ➢ Logical ➢ Date/Time
  4. 4. R2 Academy Slide 4 Variables
  5. 5. Case Study Suppose you are computing the area of a circle whose radius is 3. In R, you can do this straight away as shown below: But you cannot reuse the radius or the area computed in any other computation. Let us see how variables can change the above scenario and help us in reusing values and computations. R2 AcademyWhat is a Variable? Slide 5 ➢ Variables are the fundamental elements of any programming language. ➢ They are used to represent values that are likely to change. ➢ They reference memory locations that store information/data. Let us look at a simple case study to understand variables. > 3.14 * 3 * 3 [1] 28.26
  6. 6. R2 AcademyCreating Variables Slide 6 ASSIGNMENT OPERATOR VARIABLE NAME VARIABLE VALUE radius <- 3 We can store the value of the radius by creating a variable and assigning it the value. In this case, we create a variable called radius and assign it the value 3. In the next slide, we will see how to use this variable in computing the area of a circle.
  7. 7. R2 AcademyUsing Variables Slide 7 We use variable to store value of radius and pi and use them to compute the area of the circle. The area computed is itself stored in another variable called area.
  8. 8. R2 AcademyComponents Of A Variable Slide 8 Components Name Memory Address Value Data Type radius 0x6d8d8c8 3 Numeric
  9. 9. R2 Academy Slide 9 Naming Conventions Name must begin with a letter. Do not use numbers, dollar sign ($) or underscore ( _ ). The name can contain numbers or underscore. Do not use dash (-) or period (.). Do not use names of keywords and avoid using the names of built-in functions. Variables are case sensitive, so average and Average would be different variables. Use names that are descriptive. Generally, variable names should be nouns. If name is made of more than one word, use underscore ( _ ) to separate them.
  10. 10. R2 Academy Slide 10 ✓ Variables are the building blocks of a programming language ✓ Variables reference memory locations that store information/data ✓ An assignment operator assigns value to a variable. ✓ A variable has the following components: ○ Name ○ Memory Address ○ Value ○ Data Type ✓ Certain rules must be followed while naming variables Recap..
  11. 11. R2 Academy Slide 11 Data Types
  12. 12. R2 AcademyData Types Slide 12 Data Numeric Integer Character Logical Date/Time 1.25 1 "hello" TRUE "2015-10-05 11:41:06 IST"
  13. 13. R2 AcademyNumeric Slide 13 In R, numbers are represented by the type numeric. We will first create a variable and assign it a value. After that, we will learn a few methods of checking the type of the variable:
  14. 14. R2 AcademyNumeric Slide 14 If you have carefully observed, integers are also treated as type numeric. We will learn to create variables of type integer in a short while. We also learnt a couple of new built in functions: ➢ class Since R is an object oriented programming language, everything we create, whether it is a variable or a function, is an object that belongs to a certain class. Hence, the class function returns the class/type of the variable. ➢ is.numeric is.numeric tests whether the variable is of type numeric. Note that while the class function returns the data type, is.numeric returns TRUE or FALSE.
  15. 15. R2 AcademyInteger Slide 15 Unless specified otherwise, integers are treated as type numeric. In this section, we will learn to create variables of the type integer and to convert other data types to integer. ➢ First we create a variable number1 and assigned it the value 3 but when we use the class function, we can see that R treats number1 as type numeric and not integer. ➢ We then use as.integer to create a second variable number2. Since we have specified that the variable is of type integer, R treats number2 as integer. ➢ After that, we use is.integer to test if number1 and number2 are integers.
  16. 16. R2 AcademyInteger Slide 16
  17. 17. R2 AcademyInteger Slide 17 ➢ In the last part, we coerce other data types to type integer using as.integer.
  18. 18. R2 AcademyCharacter Slide 18 Letters, words and group of words are represented by the type character. All data of type character must be enclosed in single or double quotation marks. In fact, any value enclosed in quotes, will be treated as character type. ➢ First we create two variables first_name and last_name. In the first case, the value assigned was enclosed in double quotes, while in the second case the value assigned was enclosed in single qoutes. ➢ In the next case, we do not use any quotes and R returns an error. Hence, always ensure that you use single or double quotes while creating variables of type character. ➢ After that, we use is.character to test if last_name is of type character.
  19. 19. R2 AcademyCharacter Slide 19
  20. 20. R2 AcademyCharacter Slide 20 ➢ In the last part, we coerce other data types to type character using as.character.
  21. 21. R2 AcademyLogical Slide 21 Logical data types take only two values. Either TRUE or FALSE. Such data types are created when we compare two objects in R using comparison and logical operators. ➢ First we create two variables x and y. They are assigned the values TRUE and FALSE. After that, we use is.logical to check if they are of type logical. ➢ In the next case, we use comparison operators and see that their result is always a logical value. ➢ Finally, we coerce other data types to type logical using as.logical and see the outcome.
  22. 22. R2 AcademyLogical Slide 22
  23. 23. R2 AcademyLogical Slide 23 TRUE is represented by all numbers except 0. FALSE is represented only by 0 and no other numbers
  24. 24. R2 AcademyLogical Slide 24 We coerce other data types to type logical using as.logical.
  25. 25. R2 AcademyDate/Time Slide 25 Dates and time are represented by the data type date. We will briefly discuss ways to represent data that contain dates and time. Use as.Date to coerce data to type date.
  26. 26. R2 AcademyDate/Time Slide 26 In fact, there are a couple of other ways to represent date and time.
  27. 27. R2 Academy Slide 27 ● Numeric, Integer, Character,Logical and Date are the basic data types in R. ● class/typeof functions returns the data type of an object. ● is.data_type tests whether an object is of the specified data type ○ is.numeric ○ is.integer ○ is.character and ○ is.logical ● as.data_type will coerce objects to the specified data type ○ as.numeric ○ as.integer ○ as.character and ○ as.logical Summary
  28. 28. R2 AcademyNext Steps... Slide 28 In the next module: ✓ Understand the concept of vectors ✓ Create vectors of different data types ✓ Coercion of different data types ✓ Perform simple operations on vectors ✓ Handling missing data ✓ Learn to index/subset vectors
  29. 29. R2 Academy Slide 29 Visit Rsquared Academy for tutorials on: → R Programming → Business Analytics → Data Visualization → Web Applications → Package Development → Git & GitHub

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