Merging multiple data frames in a loop

Question

I have such a data frame(df) with ID's

I have such data frames df1 and df2:

df1:

ID  x
3   656
5   678

df2:

I want to merge df1 and df2 onto df. The resulting data frame will be:

In my real problem, I have a lot of data frames to merge with df(df also have a lot of more ID's). I want to this merging procedure in a loop. How can I do that in R? I will bevery glad for any help. Thanks a lot.

Your example, in which all dataframes contain only one column called x besides the id, it looks like you don't actually need to merge, just to bind the rows together (unless you want to keep observations with no value in x as NA). Look at rbind_all. — coffeinjunky
– coffeinjunky, Commented Feb 25, 2016 at 21:59
using dplyr library you can do just df %>% left_join(df1) %>% left_join(df2) or maybe bind_rows(df1, df2) if you dont need rows where x is NA — inscaven
– inscaven, Commented Feb 26, 2016 at 9:59

dmontaner · Accepted Answer · 2016-02-26 09:55:02Z

1

You can try something like this:

create the 'x' column with all NA values in your first data.frame

df[,"x"] <- NA

use your ID column to name the rows of your first data.frame

rownames (df) <- df$ID

and then use this rownames to replace the 'x' column just in the desired rows depending of each of your other datasets

df[df1$ID, "x"] <- df1$x

df[df2$ID, "x"] <- df2$x

This will keep the NA values in the 'x' column as in your example.

edited Feb 26, 2016 at 9:55

answered Feb 25, 2016 at 22:30

dmontaner

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