Replace string 'NULL' with NA

Question

MOst search results give me the reverse of this, turn NULL or NA into a string 'NA'. I don't want that, I want to turn string instances of 'NULL' into NA but am getting an error:

bla <- c('foo', 'bar', NA, 'NULL')

str_replace_all(bla, 'NULL', NA)
Error: `replacement` must be a character vector

Also tried:

str_replace_all(bla, 'NULL', NA_real_)
Error: `replacement` must be a character vector

How can I convert cases of 'NULL' into NA in bla?

[edit]

To be explicit, I'm actually doing this within a dplyr chain e.g.

bla <- data.frame(s = c('foo', 'bar', NA, 'NULL'), n = 1:4 )
> bla
     s n
1  foo 1
2  bar 2
3 <NA> 3
4 NULL 4
> bla %>% mutate(s = str_replace_all(bla, 'NULL', NA_real_))
Error: Problem with `mutate()` input `s`.
x `replacement` must be a character vector
ℹ Input `s` is `str_replace_all(bla, "NULL", NA_real_)`.

I reopened the post as the post is about usage of `str_replace` and `NA` — akrun, Jul 11 '21 at 04:56

akrun · Accepted Answer · 2021-07-10T23:02:28.567

Just use == instead of regex substring replacement

bla[bla == "NULL"] <- NA

-output

bla
[1] "foo" "bar" NA    NA

With str_replace/str_replace_all, specify the correct type for NA (as by default, NA is logical which would have a type clash with the original vector type

According to ?NA

NA is a logical constant of length 1 which contains a missing value indicator. NA can be coerced to any other vector type except raw. There are also constants NA_integer_, NA_real_, NA_complex_ and NA_character_ of the other atomic vector types which support missing values: all of these are reserved words in the R language.

str_replace_all(bla, 'NULL', NA_character_)
[1] "foo" "bar" NA    NA

Also, str_replace are mostly used for substring replacement and not for fixed complete string replacement (as we may find a decrease in efficiency as well)

In the tidyverse, there is also na_if

library(dplyr)
bla %>% 
    mutate(s = na_if(s, "NULL"))
     s n
1  foo 1
2  bar 2
3 <NA> 3
4 <NA> 4

Replace string 'NULL' with NA

1 Answers1