r - Subset with unique cases, based on multiple columns -
 i'd subset dataframe include rows have unique combinations of 3 columns. situation similar 1 presented in this  question, i'd preserve other columns in data well. here's example:  > df v1 v2 v3 v4 v5 1 7 1 100 98 2 7 2 98 97 3 8 1 c na 80 4 8 1 c 78 75 5 8 1 c 50 62 6 9 3 c 75 75  the requested output this, i'm looking unique cases based on v1, v2, , v3 only:  > df.new v1 v2 v3 v4 v5 1 7 1 100 98 2 7 2 98 97 3 8 1 c na 80 6 9 3 c 75 75  if recover non-unique rows great too:  > df.dupes v1 v2 v3 v4 v5 3 8 1 c na 80 4 8 1 c 78 75 5 8 1 c 50 62  i saw related question how in sql ( here ), can't in r. i'm sure it's simple messing unique() , subset() hasn't been fruitful. in advance.     you can use duplicated()  function find unique combinations:  > df[!duplicated(df[1:3]),] v1 v2 v3 v4 v5 1 7 1 100 98 2 7 2 98 97 3 8 1 c na 80 6 9 3 c 75 75  to duplicates, can check in both directions:  > df[duplicated(df[1:3]) | duplicated(df[1:3], fromlast...