Variables in R
A variable is a named memory location where we can keep values for a specific program. In simpler terms, a variable is a name that points to a memory location.
A variable is also called an identifier and is used to store a value.
Creating Variables in R
In R, do not need to declare a variable explicitly. When a value is assigned to a variable, it is automatically declared.
To assign a value to a variable, use the <- symbol. To print the variable value, just type the variable name.
Syntax:
variable_name <- value
Example
Filename: variables.R
# creating variables
sname <- "Naveen"
sage <- 20
# printing variables
sname
sage
Output:
Rscript variables.R
[1] "Naveen"
[1] 20
In the above example, sname and sage are variables, while "Naveen" and 20 are values.
In R, unlike other programming languages, you don't need to use a function to display or print variables. You can simply write the variable's name.
However, R does have a print() function to print/output variables. This might be useful if you are familiar with other programming languages, such as Python.
Example
Filename: variables_p.R
# creating variables
sname <- "Naveen"
sage <- 20
# printing variables
print (sname)
print (sage)
Output:
Rscript variables_p.R
[1] "Naveen"
[1] 20
Remainders
In many programming languages, the = sign is typically used for assigning values. But in R, you can use both = and <- for assignments. Most of the time, though, it's better to use <- since there are some cases in R where using = might not be allowed.
You can choose whether or not to use the print() function to display output of your code. But if your code is within an R expression (like inside curly braces {}), you should use the print() function to display the result.
Rules for Naming Variables in R
In R, a variable can be given a simple name, such as a or b, or it can have a more detailed name like first_name, age, or fullname.
There are some rules for naming variables in R:
- A variable name must begin with a letter or a period (
.) and can be followed by letters, numbers, a period (.), or an underscore (_). - If the variable starts with a period (
.), it cannot be followed by a digit. - A variable name cannot start with an underscore (
_) or a number. - Variable names are case-sensitive (i.e., variables
aandAare different). - Reserved words are not allowed for use as variable names (
if,TRUE,NULL, etc.).
Examples for Valid Variable Names
firstname <- "Naveen"
first_name <- "Naveen"
firstName <- "Madhu"
FIRSTNAME <- "Madhu"
name1 <- "Durga"
.fname <- "Durga"
Examples for Invalid Variable Names
first name <- "Naveen"
first-name <- "Naveen"
first@Name <- "Madhu"
_FNAME <- "Madhu"
1name <- "Durga"
.1name <- "Durga"
Multiple Variables
R allows us to assign a single value to multiple variables in one line.
Syntax:
var1 <- var2 <- var3 <- value
Example
Filename: variables_m.R
# Assign one value to multiple variables in a single line
a <- b <- c <- 10
# Print variable values
print (a)
print (b)
print (c)
Output:
Rscript variables_m.R
[1] 10
[1] 10
[1] 10