How to Check If Variable (Object) Exists in R

In R, you can check if a variable exists using the exists() function. This function tests whether an object (like a variable) exists in the current environment or in a specified environment.

Syntax

exists(name)

Parameters

name: It is the name of the object to check for existence.

Return value

It returns a logical value TRUE if the object exists and FALSE otherwise.

Example 1: Basic usage

Usage of exists() function

string <- "Hello"

exists("string")
exists("log")
exists("World")

Output

[1] TRUE
[1] TRUE
[1] FALSE

Example 2: Checking if a vector exists

Checking if a vector exists

vec <- c(1, 3, 3, 4)

exists("vec")

Output

[1] TRUE

Example 3: Checking if a data frame exists

Checking if a data frame exists

df <- data.frame(
   col1 = c(1, 2, 3),
   col2 = c(4, 5, 6)
)

exists("df")

Output

[1] TRUE

Example 4: Checking if a function exists

Let’s check the existence of rbind.fill() function from the plyr package. It will return FALSE because the rbind.fill() is not a built-in function; it is a library function.

exists("rbind.fill")

Output

[1] FALSE

To use this function, we have to import the library first.

library("plyr")

exists("rbind.fill")

Output

TRUE

Example 5: Checking if an object exists in a specific environment

var <- 1

env <- new.env()
env$var <- 21

exists("var", where = env)
exists("var", where = globalenv())

Output

[1] TRUE
[1] TRUE

You can see that the exists() function only checks for the existence of an object and not for its value. So, it will return TRUE even if the object has a value of NULL.

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