[R] Conditional selection of rows

[Gabor Grothendieck]

F Z <gerifalte28 <at> hotmail.com> writes:

: 
: 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.
: 


Try this:

   do.call("rbind", by(data, dat$Iteration, tail, 1))