R if…else Statement

In this article, you will learn to create if and if…else statement in R programming with the help of examples.

Decision making is an important part of programming. This can be achieved in R programming using the conditional if...else statement.


R if statement

The syntax of if statement is:

if (test_expression) {
statement
}

If the test_expression is TRUE, the statement gets executed. But if it’s FALSE, nothing happens.

Here, test_expression can be a logical or numeric vector, but only the first element is taken into consideration.

In the case of numeric vector, zero is taken as FALSE, rest as TRUE.

Flowchart of if statement


Flowchart of if in R Programming

Example: if statement


x <- 5
if(x > 0){
print("Positive number")
}

Output

[1] "Positive number"

if…else statement

The syntax of if…else statement is:

if (test_expression) {
statement1
} else {
statement2
}

The else part is optional and is only evaluated if test_expression is FALSE.

It is important to note that else must be in the same line as the closing braces of the if statement.

Flowchart of if…else statement


Flowchart of if...else in R Programming

Example of if…else statement


x <- -5
if(x > 0){
print("Non-negative number")
} else {
print("Negative number")
}

Output

[1] "Negative number"

The above conditional can also be written in a single line as follows.

if(x > 0) print("Non-negative number") else print("Negative number")

This feature of R allows us to write construct as shown below.

> x <- -5
> y <- if(x > 0) 5 else 6
> y
[1] 6

if…else Ladder

The if…else ladder (if…else…if) statement allows you execute a block of code among more than 2 alternatives

The syntax of if…else statement is:

if ( test_expression1) {
statement1
} else if ( test_expression2) {
statement2
} else if ( test_expression3) {
statement3
} else {
statement4
}

Only one statement will get executed depending upon the test_expressions.

Example of nested if…else


x <- 0
if (x < 0) {
print("Negative number")
} else if (x > 0) {
print("Positive number")
} else
print("Zero")

Output

[1] "Zero" 

There is an easier way to use if…else statement specifically for vectors in R programming.

You can use ifelse() function instead; the vector equivalent form of the if…else statement.


Check out these related examples: