[R] Conditional selection of rows

[F Z]

Hi,

I have a data.frame with several variables and 50,000 observations.
i.e.
data[1:2,1:7]
  Iteration Day Production.Type tsUSusc tsASusc tsULat tsALat
         1   0         Generic   17965 8833053      0      0
         1   1         Generic   17965 8833053      0      0
         .
         .
         .
         1 199         Generic   17237 8141028     26  23131
         2 127         Generic   15828 7307583     92  63463

I would like to extract only the observations (rows) for the last "day" for 
each "iteration" and store them in a data frame.

I tried lapply nested in a for loop without success.  Any help will be 
greatly appreciated!

Thanks

Francisco


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