How to use dplyr mutate to create new columns from inputting one column into a function that returns a list?

Question

I know the title is a mouthful. I have a function that returns a list. I would like to use dplyr mutate to put each value in the column through the function and put the items in the list returned into new columns.

My example:

I am working on the list using the function. Inside the function, I am using the mutate which a part of dplyr package. I am using them to put each value of the column to the list using the function. and finally, the list returns the new column.

library(dplyr)

my_df <- data_frame(filename = c("file1","file2","file3","file4"),

                    digits_only = c("10101010", "11011011", "10011000","11111111"))

compress_it_list <- function(txt) {

  len.raw <- sum(nchar(txt))

  len.xz <- length(memCompress(txt, "x"))

  len.gz <- length(memCompress(txt, "g"))

  len.bz2 <- length(memCompress(txt, "b"))

  return(list("len_raw" = len.raw, 

              "len_xz" = len.xz, 

              "len_gz" = len.gz, 

              "len_bz2" = len.bz2, 

              "min_compression" = min(c(len.raw, len.xz, len.gz, len.bz2))))

}

I can use the function to return the data frame but it's happening.

compress_it_df <- function(txt) {

  len.raw <- sum(nchar(txt))

  len.xz <- length(memCompress(txt, "x"))

  len.gz <- length(memCompress(txt, "g"))

  len.bz2 <- length(memCompress(txt, "b"))

  return(data_frame("len_raw" = len.raw, 

                    "len_xz" = len.xz, 

                    "len_gz" = len.gz, 

                    "len_bz2" = len.bz2, 

                    "min_compression" = min(c(len.raw, len.xz, len.gz, len.bz2))))

}

So I made the changes as shown:

new_df <- my_df %>%

  mutate_at(.vars = digits_only, .funs = compress_it_list)

Answer 1

you can use unnest_wider:

library(dplyr)

library(tidyr)

library(purrr)

my_df %>%

      mutate(new = map(digits_only, compress_it_list)) %>% 

      unnest_wider(c(new))

# A tibble: 4 x 7

#  filename digits_only len_raw len_xz len_gz len_bz2 min_compression

#  <chr>    <chr>         <int>  <int>  <int>   <int>           <int>

#1 file1    10101010          8     60     12      39               8

#2 file2    11011011          8     60     13      39               8

#3 file3    10011000          8     60     16      39               8

#4 file4    11111111          8     64     11      39               8

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