Variable is memory location for storing values in any programming language including R. In R Program variable names are assigned with symbol left arrow (<-) or right arrow (->) on either side or with equal to (=) symbol.
Variables are of 2 types based on their usage across the function
- Global Variable – Accessible from outside a function and is assigned with the symbol (<<-)
- Local Variable – Accessible only from inside a function and is assigned with the symbol (<-)
Based on the type of values they contain; variables can be classified as:
Boolean Variable
These variable have a binary value [1,0], [TRUE, FALSE], [YES, NO].
Example:
X= YES
Y= FALSE
Integer Variable
R has mostly numeric integer variable for declaration
Example:
X =5
Y = 7.5321
Character Variable
These variables are defined in quotation marks and contains either numeric or character values
Example:
X=” A”
Y= “9”
String Variable
These variables contain both numeric and character values with more than one value
Example:
M=”ABC”
N=”324”
Naming Convention of Variable
- A variable name consists of numbers, letters, dot, underline characters
- A variable name starts with a letter or a dot not followed by a number
- A variable name cannot start with a number.
- A variable name cannot start with an underscore character.
Create a variable
Create a dataset
Stadium <- c (“Wankhede”, “Eden Gardens”)
Audience <- c (80000, 90000)
Ticket <- c (3000, 5000)
Df <- data.frame (Stadium, Audience, Ticket)
Add a new variable: Df$stands <- c( 15, 12)
Rename an existing variable: Df$Arena <- Df$Stand
Delete a variable: DF$Arena <- NULL
Constants:
Constants are assigned with values which cannot be changed. These are of 2 types (i) Numeric Constant (ii) Character Constant
Numeric Constant: They can be of type integer, double, complex
Character Constant: They are represented by using single quotes or double quotes.
Typeof () function is used to identify the type of constant
Example:
Typeof(12) – “double”
Typeof(12L) – “integer”
Typeof(12i)— “complex”
Typeof(“12) – “character”