[R] Find all duplicate records

Erik Svensson erik.b.svensson at gmail.com
Sun Oct 2 16:05:11 CEST 2011


Hello,
In a data frame I want to identify ALL duplicate IDs in the example to be
able to examine "OS" and "time".

(df<-data.frame(ID=c("userA", "userB", "userA", "userC"),
  OS=c("Win","OSX","Win", "Win64"),
  time=c("12:22","23:22","04:44","12:28")))

     ID    OS  time
1 userA   Win 12:22
2 userB   OSX 23:22
3 userA   Win 04:44
4 userC Win64 12:28

My desired output is that ALL records with the same IDs are found:

userA   Win 12:22
userA   Win 04:44

preferably by returning logical values (TRUE FALSE TRUE FALSE)

Is there a simple way to do that?

[-- With duplicated(df$ID) the output will be
[1] FALSE FALSE  TRUE FALSE 
i.e. not all user A records are found

With unique(df$ID)
[1] userA userB userC
Levels: userA userB userC 
i.e. one of each ID is found --]

Erik Svensson

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