Creating Variables in R

Variables are containers for storing data values.

R does not have a command for declaring a variable. A variable is created the moment you first assign a value to it. To assign a value to a variable, use the <- sign. To output (or print) the variable value, just type the variable name:

Example

name <- "John"
age <- 40

name   # output "John"
age    # output 40

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From the example above, name and age are variables, while "John" and 5 are values.

In other programming language, it is common to use = as an assignment operator. In R, we can use both = and <- as assignment operators.

However, <- is preferred in most cases because the = operator can be forbidden in some context in R.

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Print / Output Variables

Compared to many other progamming languages, you do not have to use a function to print/output variables in R. You can just type the name of the variable:

Example

name <- "John Doe"

name # auto-print the value of the name variable

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However, R does have a print() function available if you want to use it. This might be useful if you are familiar with other programming languages, such as Python, which often use a print() function to output variables.

Example

name <- "John Doe"

print(name) # print the value of the name variable

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And there are times you must use the print() function to output code, for example when working with for loops (which you will learn more about in a later chapter):

Example

for (x in 1:10) {
  print(x)
}

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Conclusion: It is up to your if you want to use the print() function or not to output code. However, when your code is inside an R expression (for example inside curly braces {} like in the example above), use the print() function if you want to output the result.

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Concatenate Elements

You can also concatenate, or join, two or more elements, by using the paste() function.

To combine both text and a variable, R uses comma (,):

Example

text <- "awesome"

paste("R is", text)

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You can also use , to add a variable to another variable:

Example

text1 <- "R is"
text2 <- "awesome"

paste(text1, text2)

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For numbers, the + character works as a mathematical operator:

Example

num1 <- 5
num2 <- 10

num1 + num2

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If you try to combine a string (text) and a number, R will give you an error:

Example

num <- 5
text <- "Some text"

num + text

Result:

Error in num + text : non-numeric argument to binary operator

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Multiple Variables

R allows you to assign the same value to multiple variables in one line:

Example

# Assign the same value to multiple variables in one line
var1 <- var2 <- var3 <- "Orange"

# Print variable values
var1
var2
var3

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Variable Names

A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume). Rules for R variables are:

• A variable name must start with a letter and can be a combination of letters, digits, period(.)
  and underscore(_). If it starts with period(.), it cannot be followed by a digit.
• A variable name cannot start with a number or underscore (_)
• Variable names are case-sensitive (age, Age and AGE are three different variables)
• Reserved words cannot be used as variables (TRUE, FALSE, NULL, if...)

# Legal variable names:
myvar <- "John"
my_var <- "John"
myVar <- "John"
MYVAR <- "John"
myvar2 <- "John"
.myvar <- John

# Illegal variable names:
2myvar <- "John"
my-var <- "John"
my var <- "John"
_my_var <- "John"
my_v@ar <- "John"
TRUE <- "John"

Remember that variable names are case-sensitive!