Merge two datasets of different lengths, R

Question

I have an issue merging two datasets of different lengths - below are some examples

df1:

A B C D  E  F
1 1 1 10 20 3
1 1 1 10 20 2
1 1 1 15 10 1
1 1 1 20 15 3
1 2 1 10 20 3
1 2 1 15 10 3
2 1 1 20 20 3
2 1 1 30 10 1
2 2 1 50 10 2

df2:

A B C X  Y  Z
1 1 1 10 10 1
1 2 1 20 20 2
2 1 1 10 20 1
2 2 1 20 20 2

I need to create a new dataframe where I incorporate df2$X and df2$Y into df1 for each grouping variable (A and B).

I have tried the following:

df3 <- merge(df2, df1, all.y = TRUE)

This works as far df3$X and df3$Y are concerned, however the ordering of df3$D and df3$E is slightly wrong.

Do you have any suggestions as to how I can keep the ordering for these variables correct as they first appear in df1?

Please supply [a reproducible example](http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example). — Thomas, Jun 23 '14 at 15:31

score 2 · Answer 1 · answered Jun 23 '14 at 15:45

2

When using merge, it might be a good idea to specify a key with the following

df3 <- merge(df2, df1, by="your key", all.y=T)

but as it has been said a reproducible example would help

answered Jun 23 '14 at 15:45

FrançoisD

1 Answers1