Error in if/while (condition) {: missing Value where TRUE/FALSE needed

Question

I received this error message:

Error in if (condition) { : missing value where TRUE/FALSE needed

or

Error in while (condition) { : missing value where TRUE/FALSE needed

What does it mean, and how do I prevent it?

The double equals operator can't tolerate an NA on either side. If I define: x = NA and then do an if (x == NA){ ... } then this error will be thrown at runtime when the parser examines the left hand side of the double equals. To remedy this error, make sure every variable in your conditional is not NA using is.na(your_variable). — Eric Leschinski
– Eric Leschinski, Commented Apr 9, 2017 at 1:26
Amazing, this solved an issue I had with an observe() function on daterangeinputs in shiny. — fullera
– fullera, Commented Nov 11, 2020 at 0:18

Community · Accepted Answer · 2017-05-23 12:02:39Z

229

The evaluation of condition resulted in an NA. The if conditional must have either a TRUE or FALSE result.

if (NA) {}
## Error in if (NA) { : missing value where TRUE/FALSE needed

This can happen accidentally as the results of calculations:

if(TRUE && sqrt(-1)) {}
## Error in if (TRUE && sqrt(-1)) { : missing value where TRUE/FALSE needed

To test whether an object is missing use is.na(x) rather than x == NA.

See also the related errors:

Error in if/while (condition) { : argument is of length zero

Error in if/while (condition) : argument is not interpretable as logical

if (NULL) {}
## Error in if (NULL) { : argument is of length zero

if ("not logical") {}
## Error: argument is not interpretable as logical

if (c(TRUE, FALSE)) {}
## Warning message:
## the condition has length > 1 and only the first element will be used

edited May 23, 2017 at 12:02

CommunityBot

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answered Sep 8, 2011 at 22:30

Brian Diggs

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Comments

pbatey · Accepted Answer · 2017-06-02 22:49:24Z

11

I ran into this when checking on a null or empty string

if (x == NULL || x == '') {

changed it to

if (is.null(x) || x == '') {

answered Jun 2, 2017 at 22:49

pbatey

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1 Comment

Frank Over a year ago

Fyi, there's also !(length(x) == 1L && nzchar(x))

Krutik · Accepted Answer · 2022-04-20 11:26:54Z

4

I was getting this same error in my forloops with complex if statements. I fixed this issue by just wrapping my condition with isTRUE.

if(isTRUE(condition)==TRUE) {do something}

answered Apr 20, 2022 at 11:26

Krutik

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Comments

symkly · Accepted Answer · 2020-08-06 10:04:35Z

0

this works with "NA" not for NA

comments = c("no","yes","NA")
  for (l in 1:length(comments)) {
    #if (!is.na(comments[l])) print(comments[l])
    if (comments[l] != "NA") print(comments[l])
  }

answered Aug 6, 2020 at 10:04

symkly

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