R: Remove multiple empty columns of character variables

Question

I have a data frame where all the variables are of character type. Many of the columns are completely empty, i.e. only the variable headers are there, but no values. Is ther

Answer 1

This can also be done by dplyr and select_if

`select_if(df,function(x){any(!is.na(x))})`

or with is.null() or x=="" depending on how empty values are defined in your data.

Answer 2

If you're talking about columns where all values are NA, use remove_empty("cols") from the janitor package.

If you have character vectors where every value is the empty string "", you can first convert those values to NA throughout your data.frame with na_if from the dplyr package:

dat <- data.frame(
  x = c("a", "b", "c"),
  y = c("", "", ""),
  z = c(NA, NA, NA),
  stringsAsFactors = FALSE
)

dat
#>   x y  z
#> 1 a   NA
#> 2 b   NA
#> 3 c   NA

library(dplyr)
library(janitor)

dat %>%
  mutate_all(funs(na_if(., ""))) %>%
  remove_empty("cols")
#>   x
#> 1 a
#> 2 b
#> 3 c

Answer 3

If your empty columns are really empty character columns, something like the following should work. It will need to be modified if your "empty" character columns include, say, spaces.

Sample data:

mydf <- data.frame(
  A = c("a", "b"),
  B = c("y", ""),
  C = c("", ""),
  D = c("", ""),
  E = c("", "z")
)
mydf
#   A B C D E
# 1 a y      
# 2 b       z

Identifying and removing the "empty" columns.

mydf[!sapply(mydf, function(x) all(x == ""))]
#   A B E
# 1 a y  
# 2 b   z

---

Alternatively, as recommended by @Roland:

> mydf[, colSums(mydf != "") != 0]
  A B E
1 a y  
2 b   z