Select matching strings of columns from a nested list of tibbles / tidyverse / R

Question

I have a large list containing single lists of multiple tibbles. I want to select only relevant columns with purrr::map, but I get the error message that deplyr::select is not aplicable for lists. If my list only contains one tibble at a time the dplyr::select command works, as the select function recognizes the format as a tibble. So it should be quite easy to work around this error, but I can not quite get there.

The error I get is:

select() doesn't handle lists

How can I work around this, as it should be possible to write a command something like that:

cleaned_lists <- map(lists,select,matches("string1|string2|string3|string4|string5"))

Thanks in advance!

It's easier to help you if you include a simple [reproducible example](https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example) with sample input and desired output that can be used to test and verify possible solutions. — MrFlick, Nov 28 '22 at 16:03

score 2 · Accepted Answer · answered Nov 28 '22 at 17:00

If it is a nested list, we need an inner map

library(purrr)
library(dplyr)
cleaned_lists <- map(lists, map, select, 
       matches("string1|string2|string3|string4|string5"))

-Reproducible example

> lists <- list(list(mtcars, iris), list(mtcars, iris))
> map(lists, select, matches("Species|mpg"))
Error in `.f()`:
! `select()` doesn't handle lists.
Run `rlang::last_error()` to see where the error occurred.
> str(map(lists, map, select, matches("Species|mpg")))
List of 2
 $ :List of 2
  ..$ :'data.frame':    32 obs. of  1 variable:
  .. ..$ mpg: num [1:32] 21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
  ..$ :'data.frame':    150 obs. of  1 variable:
  .. ..$ Species: Factor w/ 3 levels "setosa","versicolor",..: 1 1 1 1 1 1 1 1 1 1 ...
 $ :List of 2
  ..$ :'data.frame':    32 obs. of  1 variable:
  .. ..$ mpg: num [1:32] 21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
  ..$ :'data.frame':    150 obs. of  1 variable:
  .. ..$ Species: Factor w/ 3 levels "setosa","versicolor",..: 1 1 1 1 1 1 1 1 1 1 ...

Select matching strings of columns from a nested list of tibbles / tidyverse / R

1 Answers1