In the reprex below I need to assign 'sex' and 'age' values to df2 based on the information contained in df1; however, the number and order of rows are not the same in the two dataframes, so I cannot use merge() / by=, due to there being multiple rows for some participants (as denoted by 'id'). So, I would need both rows in df2 with an id of 'b' (i.e. rows 1-2) to have a sex of 'F' and an age of 51, then the row with an id of 'd' (row 3) to have a sex of 'F' and an age of 53, etc. Any help would be greatly appreciated. Thank you.

Reprex:

df1<-
  data.frame(
    id=as.factor(print(letters[1:6])),
    sex=as.factor(rep(c("M","F"),3)),
    age=as.numeric(50:55)
    )

df2<-
  data.frame(
    id=as.factor(c("b","b","d","c","c","c","a","e","e","f"))
  )

In the reprex below I need to assign 'sex' and 'age' values to df2 based on the information contained in df1; however, the number and order of rows are not the same in the two dataframes, so I cannot use merge() / by=, due to there being multiple rows for some participants (as denoted by 'id'). So, I would need both rows in df2 with an id of 'b' (i.e. rows 1-2) to have a sex of 'F' and an age of 51, then the row with an id of 'd' (row 3) to have a sex of 'F' and an age of 53, etc. Any help would be greatly appreciated. Thank you.

Reprex:

df1<-
  data.frame(
    id=as.factor(print(letters[1:6])),
    sex=as.factor(rep(c("M","F"),3)),
    age=as.numeric(50:55)
    )

df2<-
  data.frame(
    id=as.factor(c("b","b","d","c","c","c","a","e","e","f"))
  )

• r

1 Answer 1

Isn't this what you want? It's exactly what merge is for..

> merge(df2, df1, by="id",sort = FALSE)
   id sex age
1   b   F  51
2   b   F  51
3   d   F  53
4   c   M  52
5   c   M  52
6   c   M  52
7   a   M  50
8   e   M  54
9   e   M  54
10  f   F  55