How to Join Multiple Data Frames Using dplyr

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Often you may be interested in joining multiple data frames in R. Fortunately this is easy to do using the left_join() function from the dplyr package.

library(dplyr)

For example, suppose we have the following three data frames:

#create data frame
df1 

To join all three data frames together, we can simply perform two left joins, one after the other:

#join the three data frames
df1 %>%
    left_join(df2, by='a') %>%
    left_join(df3, by='a')

   a  b  c  d
1  a 12 23 NA
2  a 12 24 NA
3  a 12 33 NA
4  b 14 34 NA
5  b 14 37 NA
6  b 14 41 NA
7  c 14 NA NA
8  d 18 NA 23
9  e 22 NA 24
10 f 23 NA 33

Note that you can also save the result of this join as a data frame:

#join the three data frames and save result as new data frame named all_data
all_data %
              left_join(df2, by='a') %>%
              left_join(df3, by='a')

#view summary of resulting data frame
glimpse(all_data)

Observations: 10
Variables: 4
$ a  "a", "a", "a", "b", "b", "b", "c", "d", "e", "f"
$ b  12, 12, 12, 14, 14, 14, 14, 18, 22, 23
$ c  23, 24, 33, 34, 37, 41, NA, NA, NA, NA
$ d  NA, NA, NA, NA, NA, NA, NA, 23, 24, 33

Additional Resources

How to Filter Rows in R
How to Remove Duplicate Rows in R
How to Group & Summarize Data in R