How to merge dataframes of two lists together (same columns)

Question

I have a list of 9 dataframes with the same columnames (called datalist) The dataframes (called L01, L02, ... L09) have all the following structure:

$L01
               time pressure    level abs_level
2021-04-22 00:00:00 21.05800 2.146454  12.33845
2021-04-22 00:15:00 21.09500 2.150225  12.34223
2021-04-22 00:30:00 21.04800 2.145435  12.33743

> str(datalist)
List of 10
 $ L01     :'data.frame':   9792 obs. of  4 variables:
  ..$ time     : POSIXct[1:9792], format: "2021-04-22 00:00:00" "2021-04-22 00:15:00" "2021-04-22 00:30:00" "2021-04-22 00:45:00" ...
  ..$ pressure : num [1:9792] 21.1 21.1 21 21 21 ...
  ..$ level    : num [1:9792] 2.15 2.15 2.15 2.14 2.14 ...
  ..$ abs_level: num [1:9792] 12.3 12.3 12.3 12.3 12.3 ...
 $ L02     :'data.frame':   9792 obs. of  4 variables:
  ..$ time     : POSIXct[1:9792], format: "2021-04-22 00:00:00" "2021-04-22 00:15:00" "2021-04-22 00:30:00" "2021-04-22 00:45:00" ...
  ..$ pressure : num [1:9792] 19.4 19.4 19.3 19.3 19.3 ...
  ..$ level    : num [1:9792] 1.97 1.98 1.97 1.97 1.97 ...
  ..$ abs_level: num [1:9792] 12.4 12.4 12.4 12.4 12.4 ...

...

I have a similar addlist with the same 9 dataframes (also L01, L02, ... L09) of the same structure (same columns and same order), but these data are from a different time period. But I just want to merge the dataframes of the addlist to the datalist, so that the rows of dataframe L01 of addlist are added to the dataframe of L01 in the datalist), L02 to L02, and so on for the rest of the dataframes.

So actually very easy... I thought. I can't find the answer clearly on the internet. I was thinking of using rbind, but I don't know how to use that in the context of the two lists.

How can I do this? Any suggestions? Many thanks in advance!

jmalston · Accepted Answer · 2021-08-10 10:49:41Z

2

Does this work?

finallist <- list()

for(i in 1:length(datalist)){
    finallist[[i]] <- rbind(datalist[[i]],addlist[[i]])
}

There's probably a more efficient way to do this, but this should work if the lists you want to combine are in the same order and have the same columns

edited Aug 10, 2021 at 10:49

answered Aug 10, 2021 at 9:28

jmalston

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4 Comments

Rory S Over a year ago

You aren't assigning the result of rbind to anything here; surely you'd need to initialize a "results" list and then store the bound dataframes in that?

jmalston Over a year ago

Yep--just edited it and checked it with two objects in my current R environment to make sure it works this time

Ronak Shah Over a year ago

Are you sure this works? I think this will overwrite finallist in every iteration. Lastly, finallist will have output for only last combination.

jmalston Over a year ago

Correct again, thanks--just updated to fix that (I used a list of 1 to test)

ThomasIsCoding · Accepted Answer · 2021-08-10 09:44:27Z

2

You can try the base R code below

Map(rbind, datalist, addlist)

answered Aug 10, 2021 at 9:44

ThomasIsCoding

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Pedro Alencar · Accepted Answer · 2021-08-10 09:34:09Z

1

you can use

df <- do.call('rbind', your_list)

or

library(data.table)

df <- rbindlist(your_list)

answered Aug 10, 2021 at 9:34

Pedro Alencar

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Rory S · Accepted Answer · 2021-08-10 10:54:25Z

0

Using purrr from the tidyverse, you could try:

library(purrr)
map2(datalist, addlist, ~ rbind(.x, .y))

answered Aug 10, 2021 at 10:54

Rory S

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