How to rbind sublists in R

Question

I have a list of lists of dataframes. What I am trying to do can be described by the following:

rbind(datalistpairs[[1]][[1]][[1]],datalistpairs[[1]][[2]][[1]],datalistpairs[[1]][[3]][[1]])

My sublist has j length so in reality I am trying something like (for j times):

rbind(datalistpairs[[1]][[1]][[1]],
datalistpairs[[1]][[2]][[1]],
datalistpairs[[1]][[3]][[1]],...,
datalistpairs[[1]][[j]][[1]])

What is the most efficient way to do it?

The output with three iterations creates an dataframe which looks like this:

      LAT    LON
   31  43.1818 5.2348
   311 43.1818 5.2348
   312 43.1818 5.2348

EDIT: I provide below sample data

datalistpairs = list(list(list(l1 = data.frame(LAT = 1, LON = 2), 
                               l2 = data.frame(LAT = 1, LON = 2)),
                          list(l1 = data.frame(LAT = 1, LON = 2), 
                               l2 = data.frame(LAT = 1, LON = 2))),
                     list(list(l1 = data.frame(LAT = 1, LON = 2), 
                               l2 = data.frame(LAT = 1, LON = 2)),
                         list(l1 = data.frame(LAT = 1, LON = 2), 
                              l2 = data.frame(LAT = 1, LON = 2))))

and my goal is to get:

rbind(datalistpairs[[1]][[1]][[1]],datalistpairs[[1]][[2]][[1]])

Hope this helps.

Please provide [minimal reproducible data](https://stackoverflow.com/q/5963269/10068985) for us to test the output. — Darren Tsai, May 14 '20 at 11:06
@DarrenTsai Sorry, I didn't mean to offend anyone with my comment. — jay.sf, May 14 '20 at 13:04

Darren Tsai · Accepted Answer · 2020-05-14T12:27:23.913

3

Use map() to extract the first element of each sublist.

library(purrr)

datalistpairs[[1]] %>% map_dfr(~ .[[1]])

#   LAT LON
# 1   1   2
# 2   1   2

The corresponding base R solution:

do.call(rbind, lapply(datalistpairs[[1]], `[[`, 1))

Edit: How to apply to datalistpairs[[i]] where i = 1, 2, 3, ..., n

lapply(1:n, function(i){
  do.call(rbind, lapply(datalistpairs[[i]], `[[`, 1))
})

edited May 14 '20 at 12:27

answered May 14 '20 at 11:36

Darren Tsai

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Thank you Darren. Your solution is really elegant. To some extend how your solution can be best applied to datalistpairs[[i]] where i = 1, 2, 3, .... n? Same idea? – Stylianos Z. May 14 '20 at 12:22
Amazing! Thank you. – Stylianos Z. May 14 '20 at 12:29

How to rbind sublists in R

1 Answers1