Combine two lists in a dataframe in R

Question

I have two lists with different structure:

listA <- list(c("a","b","c"), c("d","e"))
listB <- list(0.05, 0.5)

listA
[[1]]
[1] "a" "b" "c"

[[2]]
[1] "d" "e"

listB
[[1]]
[1] 0.05

[[2]]
[1] 0.5

I have an idea of how to use looping to combine both lists in a dataframe that looks like the one below but I'm sure that there is a more efficient way of doing this.

data.frame(A = c("a","b","c","d","e"), B = c(rep(0.05,3), rep(0.5,2)))
  A    B
1 a 0.05
2 b 0.05
3 c 0.05
4 d 0.50
5 e 0.50

Matthew Plourde · Accepted Answer · 2015-02-20T22:10:08.373

37

This is another option:

do.call(rbind, Map(data.frame, A=listA, B=listB))

#   A    B
# 1 a 0.05
# 2 b 0.05
# 3 c 0.05
# 4 d 0.50
# 5 e 0.50

edited Feb 20 '15 at 22:10

answered Feb 20 '15 at 13:41

Matthew Plourde

43,932
7
96
113

Rentrop · Answer 2 · 2015-02-20T22:32:21.237

5

Maybe there is a more elegant way that keeps the class numeric of list2's elements... But this one works as well

df <- do.call(rbind,mapply(cbind, listA, listB))
df <- as.data.frame(df, stringsAsFactors = FALSE)
df[,2] <- as.numeric(df[,2])

EDIT Way better is Matthew Plourde's solution using Map aka mapply(data.frame, A=listA, B=listB, SIMPLIFY = FALSE)

edited Feb 20 '15 at 22:32

answered Feb 20 '15 at 13:30

Rentrop

20,979
10
72
100

score 4 · Answer 3 · answered Feb 12 '19 at 22:43

4

If looking for a tidyverse solution, here is the analogue to the accepted answer. Using the dfr suffix to the map function family enables a very simple solution which should also be faster than do.call("rbind").

library(tidyverse)
listA <- list(c("a","b","c"), c("d","e"))
listB <- list(0.05, 0.5)

map2_dfr(listA, listB, ~ tibble(A = .x, B = .y))
#> # A tibble: 5 x 2
#>   A         B
#>   <chr> <dbl>
#> 1 a      0.05
#> 2 b      0.05
#> 3 c      0.05
#> 4 d      0.5 
#> 5 e      0.5

^{Created on 2019-02-12 by the reprex package (v0.2.1)}

answered Feb 12 '19 at 22:43

Calum You

14,687
4
23
42

best solution because there are no ugly row names! – Peter Apr 04 '20 at 19:35
@ Calum You can you explain the meaning of .x and .y? Which letters beside .x and .y should I use if I have lists A,B,C and D instead of only A and B? Thank you! – user2165379 Mar 19 '23 at 13:03
@user2165379 see the documentation for map2; .x and .y are placeholders for the first and second arguments to the function. you'll want pmap for arbitrary argument number functions and ..1, ..2 placeholders. – Calum You Mar 20 '23 at 07:30
@ Calum You thank you. I will look into pmap. – user2165379 Mar 20 '23 at 12:44

score 3 · Answer 4 · answered Nov 28 '19 at 03:58

3

Another way without using do.call:

cbind(data.frame(listA), data.frame(listB))

answered Nov 28 '19 at 03:58

S.Zhong

66
3

score 2 · Answer 5 · answered Feb 20 '15 at 13:39

2

I'd prefer this:

do.call(rbind,
        Map(function(...) setNames(cbind.data.frame(...), 
                                   c("A", "B")), 
            listA, listB))
#  A    B
#1 a 0.05
#2 b 0.05
#3 c 0.05
#4 d 0.50
#5 e 0.50

answered Feb 20 '15 at 13:39

Roland

127,288
10
191
288

score 1 · Answer 6 · answered Feb 20 '15 at 13:37

1

Here is another way:

do.call(rbind,
        lapply(1:length(listA),
               function(i)
                 data.frame(A=unlist(listA[i]),
                            B=unlist(listB[i]))))

answered Feb 20 '15 at 13:37

zx8754

52,746
12
114
209

Carlo Carandang · Answer 7 · 2021-04-12T11:12:00.103

0

This places the index and renames the columns appropriately:

df <- do.call(rbind.data.frame, Map('c', listA, listB))
colnames(df)[1] <- "A"
colnames(df)[2] <- "B"

edited Apr 12 '21 at 11:12

answered Apr 06 '21 at 12:01

Carlo Carandang

187
1
8

Combine two lists in a dataframe in R

7 Answers7

Linked