How do I merge data frames in a list?

Question

I have a list of data frames. I want to merge them vertically on column name.

Here are three data frames in my list, for example:

Precinct VoterTurnout Johnson Jameson
4030     45           20      25

And this one...

Precinct VoterTurnout Jimson
1234     33           20

And the third...

Precinct VoterTurnout Jhohnshohn
4321     555          222

These dataframes are in a list named listDFs. How do I merge them to look like this?

Precinct VoterTurnout Johnson Jameson Jimson Jhohnshohn
4030     45           20      25      NA     NA
1234     33           NA      NA      20     NA
4321     555          NA      NA      NA     222

I suspect you can find an earlier answer with a search:"reduce merge dataframe ". — IRTFM, Apr 27 '17 at 16:48

Dan · Answer 1 · 2017-04-27T17:21:41.277

Using the tidyverse packages, you can use Reduce and full_join() to accomplish it:

First, let's create the "sub-tables" as tibbles:

library(tidyverse)

a <- tribble(
  ~Precinct, ~VoterTurnout, ~Johnson,
  4030,     45,           20
)

b <- tribble(
  ~Precinct, ~VoterTurnout, ~Jimson,
  1234,     33,           20
)

c <- tribble(
  ~Precinct, ~VoterTurnout,  ~Jhohnshohn,
  4321,     555,          222
)

Now that we have tables a , b, and c we can join the list recursively with Reduce:

ll <- list(a,b,c)

ll %>% 
  reduce(full_join)

Note that the NA's appear where they should when you use a full_join.

Let's inspect the result:

    # A tibble: 3 × 5
  Precinct VoterTurnout Johnson Jimson Jhohnshohn
     <dbl>        <dbl>   <dbl>  <dbl>      <dbl>
1     4030           45      20     NA         NA
2     1234           33      NA     20         NA
3     4321          555      NA     NA        222

How do I merge data frames in a list?

1 Answers1