# R ifelse() Function

In this article, you will learn about the ifelse() function in R programming with the help of examples.

Vectors form the basic building block of R programming. Most of the functions in R take vectors as input and output a resultant vector.

This vectorization of code will be much faster than applying the same function to each element of the vector individually.

Similar to this concept, there is a vector equivalent form of the if…else statement in R, the `ifelse()` function.

The `ifelse()` function is a conditional function in R that allows you to perform element-wise conditional operations on vectors or data frames.

## Syntax of ifelse() function

The syntax of the `ifelse()` function is:

``ifelse(test_expression, x, y)``

Here,

• `text_expression` - A logical condition or a logical vector that specifies the condition to be evaluated. It can be a single logical value or a vector of logical values.
• `x` - The value or expression to be returned when the condition is true. It can be a single value, vector, or an expression.
• `y` - The value or expression to be returned when the condition is false. It can be a single value, vector, or an expression.

The return value is a vector with the same length as `test_expression`.

This is to say, the `ith` element of the result will be `x[i]` if `test_expression[i]` is `TRUE` else it will take the value of `y[i]`.

### Example: ifelse() function

``````# create a vector
a = c(5,7,2,9)
# check if each element in a is even or odd
ifelse(a %% 2 == 0,"even","odd")``````

Output

`[1] "odd"  "odd"  "even" "odd" `

In the example, a is a vector with values `[5, 7, 2, 9]`.

When we apply the condition `a %% 2 == 0`, it checks each element in `a` to see if it is divisible by 2 without a remainder. This results in a logical vector: `[FALSE, FALSE, TRUE, FALSE]`.

Now, the `ifelse()` function takes this logical vector as the condition. It also takes two other vectors: `["even", "even", "even", "even"]` and `["odd", "odd", "odd", "odd"]`.

Since the condition vector has a length of 4, the other two vectors are recycled to match this length.

The `ifelse()` function then evaluates each element of the condition vector. If the element is `TRUE`, it chooses the corresponding element from the `"even"` vector. If the element is `FALSE`, it chooses the corresponding element from the `"odd"` vector.