Count NULL values by column in R

Question

I'm trying to sum the number of NULL values in my dataframe in R. I can easily do so with NA values using the code below:

colSums(is.na(df))

but when I attempt to do this with is.null I get back the following error:

Error in colSums(is.null(df)) : 'x' must be an array of at least two dimensions

I believe the solution is to change the dataframe into another form to do this - but I don't know how and internet searches have proven fruitless (and often conflate NAs and NULLs)

is.na() returns a logical matrix with the same dimensions as the data frame, whereas is.null() returns a single TRUE/FALSE value. It would help to see some or all of the data df (including the NULL values) using e.g. dput(df) or dput(head(df)). NULL may not mean what you think it means e.g. it may be stored as type character. — neilfws
– neilfws, Commented Nov 22, 2021 at 3:11

r.user.05apr · Accepted Answer · 2021-11-22 09:12:43Z

1

NULL values in data frames are actually empty lists. You have to check whether their length is 0. Either in tidyr:

library(tidyverse)

d <- tribble(~a, ~b,
             "a", NULL,
             NULL, "y",
             "b", "z")
d
# A tibble: 3 x 2
# a         b        
# <list>    <list>   
# 1 <chr [1]> <NULL>   
# 2 <NULL>    <chr [1]>
sum(map_dbl(d, ~length(~.x) > 0))
# [1] 2

or Base R:

d <- data.frame(a = I(list("a", NULL, "b")),
                b = I(list(NULL, "y", "z")))
d
# a b
# 1 a  
# 2   y
# 3 b z
sum(apply(d, 2, function(a) sum(vapply(a, function(b) length(b) == 0L, numeric(1)))))
#[1] 2

answered Nov 22, 2021 at 9:12

r.user.05apr

5,4783 gold badges27 silver badges43 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Count NULL values by column in R

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related