Dear Group,

I am working with a large dataset where I need to select for each unique id
the the unique lastpk row.  Here is a sample subject:

          id             wtdt           wt         lastpk

  64050256 2010-09-18   275  2010-09-16

  64050256 2010-09-19   277  2010-09-18

  64050256 2010-09-20   272  2010-09-18

  64050256 2010-09-21   277  2010-09-18



I want the result as:

       id               wtdt         wt      lastpk

64050256 2010-09-18 275 2010-09-16

64050256 2010-09-19 277 2010-09-18



I am using !(duplicated(data$id)) to select the first row but now I want to
select the first row of the unique lastpk in each unique id.



I appreciate your help on this.



Regards,

Ayyappa

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