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

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

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

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

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This can happen accidentally as the results of calculations:

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

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

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

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

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``if (NULL) {}n## Error in if (NULL) { : argument is of length zeronnif (not logical) {}n## Error: argument is not interpretable as logicalnnif (c(TRUE, FALSE)) {}n## Warning message:n## the condition has length > 1 and only the first element will be usedn``

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

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``if (x == NULL || x == ) {n``

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changed it to

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``if (is.null(x) || x == ) {n``

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

this works with `NA` not for `NA`

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