[SOLVED] Drop a column if all of its values are NA

Drop a column if all of its values are NA

I've got a database query running from R which can have multiple columns filled with NA, some of these columns I need further down the line but one specific column can be dropped if all values are NA.

I usually use purrr::discard(~all(is.na(.))) to drop the columns which are all NA, but since this dataframe can contain multiple columns with NA where I only want to remove one I'm struggling to make this specific to the column in a tidyverse solution.

I've currently got this workaround:

  if(sum(is.na(Orders$Originator)) == nrow(Orders)) {
    
    Orders <- Orders %>%
      select(-Originator)
    
  }

But it would improve the readability if I can have this in a tidyverse solution. Hope someone can be of help!

Thanks!

Solution

Using example data:

df <- data.frame(
  x = c(1,2,NA),
  y = NA,
  z = c(3,4,5)
)

Here column y is the target column to check if all is.na. Your if and else will be contained in curly braces. The braces will suppress the pipe from using the first argument in a function. Note the else will keep your data frame in the pipe if the condition is false.

library(tidyverse)

df %>%
  { if (all(is.na(.$y))) select(., -y) else . }

Output