duplicates in multiple columns

Question

I have a data frame like so

> df
  a  b c    d
1 1  2 A 1001
2 2  4 B 1002
3 3  6 B 1002
4 4  8 C 1003
5 5 10 D 1004
6 6 12 D 1004
7 7 13 E 1005
8 8 14 E          


        

Answer 1

It works if you use duplicated twice:

df[!(duplicated(df[c("c","d")]) | duplicated(df[c("c","d")], fromLast = TRUE)), ]

  a  b c    d
1 1  2 A 1001
4 4  8 C 1003
7 7 13 E 1005
8 8 14 E 1006

Answer 2

Make a new object with the 2 columns:

df_dups <- df[c("c", "d")]

Now apply it to your main df:

df[!duplicated(df_dups),]

Looks neater and easy to see/change columns that you are using.