In R programming, NA is a logical constant used denote a missing value. The length of NA is 1.

In this tutorial, we will learn what NA is in R programming, how to assign NA to a variable, and how to check if a value is NA or not.

Assign NA to a Variable

To assign NA to a variable x, use the following syntax.

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x <- NA

Check if Value is NA

To check if a value stored in a variable x is NA, use the following expression.

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is.na(x)

In the following program, we will assign NA to a variable x. We shall programmatically check if x is having missing value NA or not.

example.R

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x <- NA
print(is.na(x))

Output

[1] TRUE

If x is a list, then is.na(x) returns TRUE or FALSE for each item in the list.

In the following program, we will create a list with some values, and programmatically check if these are NA or not.

example.R

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x <- list("Hello", NA)
print(is.na(x))

Output

[1] FALSE  TRUE

Check if there is any NA

We can check if there is any NA in given atomic vector, list, or pairlist.

In the following program, we will take a list where an element is NA. anyNA must return TRUE, since there is at least one NA in the list.

example.R

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x <- list("Hello", NA)
print(anyNA(x))

Output

[1] TRUE

Length of NA

NA has a length of 1. Let us print the length of NA to output using length() function.

example.R

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x <- NA
print(length(x))

Output

[1] 1

Conclusion

In this R Tutorial, we learned how to find the minimum value of given arguments using min() function, with the help of examples.