Replace a specific NA value with a character in R

March 27, 2023

I feel a bit stuck, and I am looking for a clever way to replace a specific NA value with a character. Any help or guidance is appreciated!

An example data.frame would look like this

library(tidyverse)
df <- tibble(genes=c("A","B","C"), x=c(NA,NA,4), y=c(NA,3,4))
df
#> # A tibble: 3 × 3
#>   genes     x     y
#>   <chr> <dbl> <dbl>
#> 1 A        NA    NA
#> 2 B        NA     3
#> 3 C         4     4

^{Created on 2023-03-27 with reprex v2.0.2}

I want to replace when gene==A the NA value in the x column with Yes. The rest of the values in the x column should remain the same. I tried with mutate and case_when(), but I am taking an error.

I want my date to look like this

#> # A tibble: 3 × 3
#>    genes     x     y
#>   <chr>    <dbl> <dbl>
#> 1   A       Yes    NA
#> 2   B        NA     3
#> 3   C         4     4

>Solution :

You could use an ifelse with is.na and condition on genes like this:

library(tidyverse)
df %>%
  mutate(x = ifelse(is.na(x) & genes == 'A', 'Yes', x))
#> # A tibble: 3 × 3
#>   genes x         y
#>   <chr> <chr> <dbl>
#> 1 A     Yes      NA
#> 2 B     <NA>      3
#> 3 C     4         4

^{Created on 2023-03-27 with reprex v2.0.2}