Separating a List into Columns

Question

I have this list in R:

my_list = list("word",c("word", "word"), "word", c("word", "word","word"), "word")

[[1]]
[1] "word"

[[2]]
[1] "word" "word"

[[3]]
[1] "word"

[[4]]
[1] "word" "word" "word"

[[5]]
[1] "word"

I would like to convert this list into a data frame that looks something like this:

  col1 col2 col3
1 word          
2 word word     
3 word          
4 word word word
5 word   

# source code of the desired output

structure(list(col1 = c("word", "word", "word", "word", "word"
), col2 = c("", "word", "", "word", ""), col3 = c("", "", "", 
"word", "")), class = "data.frame", row.names = c(NA, -5L))

I tried to use the answer provided here (How to split a column of list into several columns using R) for my question:

z = my_list
x <- do.call(rbind, z)
colnames(x) <- LETTERS[1:ncol(x)]
h = data.frame(cbind(z[c("sg", "time")], x))

But this is not giving me the desired output.

Can someone please show me how to do this?

Thank you!

score 3 · Accepted Answer · answered Nov 29 '22 at 16:37

3

You could use lapply to make the list element lengths the same, then do.call with rbind to create the desired output:

do.call(rbind, lapply(my_list, `length<-`, max(lengths(my_list))))

Output

#      [,1]   [,2]   [,3]  
# [1,] "word" NA     NA    
# [2,] "word" "word" NA    
# [3,] "word" NA     NA    
# [4,] "word" "word" "word"
# [5,] "word" NA     NA

If you wanted there to be blanks as opposed to NA values:

new_df <- do.call(rbind, lapply(my_list, `length<-`, max(lengths(my_list))))
new_df[is.na(new_df)] <- ""

Output:

#      [,1]   [,2]   [,3]  
# [1,] "word" ""     ""    
# [2,] "word" "word" ""    
# [3,] "word" ""     ""    
# [4,] "word" "word" "word"
# [5,] "word" ""     ""

answered Nov 29 '22 at 16:37

jpsmith

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@ jpsmith : thank you for your answer! I was about to make a quick modification to your answer with the following code: – stats_noob Nov 29 '22 at 16:40
p = data.frame(do.call(rbind, lapply(my_list, `length<-`, max(lengths(my_list))))) – stats_noob Nov 29 '22 at 16:40
p[is.na(p)] <- " " – stats_noob Nov 29 '22 at 16:40
Good answer, I'd put the `max` calculation outside the loop though. – Andre Wildberg Nov 29 '22 at 16:40
# source: https://stackoverflow.com/questions/19592706/replace-missing-values-na-with-blank-empty-string – stats_noob Nov 29 '22 at 16:41
1

But it looks like you have already added this! thank you so much! – stats_noob Nov 29 '22 at 16:41

score 2 · Answer 2 · answered Nov 29 '22 at 16:43

With stringi::stri_list2matrix:

library(stringi)
data.frame(stri_list2matrix(my_list, byrow = TRUE))
#     X1   X2   X3
# 1 word <NA> <NA>
# 2 word word <NA>
# 3 word <NA> <NA>
# 4 word word word
# 5 word <NA> <NA>

Or with sapply:

t(sapply(my_list, "length<-", max(lengths(my_list))))

Separating a List into Columns

2 Answers2