Hi Felipe,
Try
x <- structure(list(Units = c(1L, 1L, 2L, 2L, 2L, 3L, 3L, 4L, 4L,
4L), Var1 = structure(c(2L, 3L, 4L, 3L, 1L, 3L, 1L, 2L, 3L, 1L
), .Label = c("A", "B", "C", "D"), class = "factor"), Var2 = c(2L,
1L, 3L, 2L, 1L, 2L, 1L, 3L, 2L, 1L), Var3 = c(2L, 3L, 3L, 1L,
2L, 1L, 3L, 3L, 2L, 1L)), .Names = c("Units", "Var1", "Var2",
"Var3"), class = "data.frame", row.names = c(NA, -10L))
do.call(rbind, lapply(with(x, split(x, Units)), function(d) d[which.max(d[,
3]),]))
# Units Var1 Var2 Var3
# 1 1 B 2 2
# 2 2 D 3 3
# 3 3 C 2 1
# 4 4 B 3 3
HTH,
Jorge.-
On Mon, Jan 16, 2012 at 5:13 PM, Felipe Nunes <> wrote:
> Dear all,
>
> I have a data set in which the same unit appears 2 or 3 or 4 times. I need
> to aggregate this data to maintain only one unit by row. But I need to do
> that based on a comparison between the values of such units. I can't find a
> function to help me on that. I appreciate any help. Below I provide an
> example of what I want:
>
> This is my data:
>
> Units Var1 Var2 Var3
> 1 B 2 2
> 1 C 1 3
> 2 D 3 3
> 2 C 2 1
> 2 A 1 2
> 3 C 2 1
> 3 A 1 3
> 4 B 3 3
> 4 C 2 2
> 4 A 1 1
>
> I want to produce a new data in which I keep, for each unit, the row with
> max number for Var2. For instance,
>
> Units Var1 Var2 Var3
> 1 B 2 2
> 2 D 3 3
> 3 C 2 1
> 4 B 3 3
>
> Thanks,
>
>
> *Felipe Nunes*
> CAPES/Fulbright Fellow
> PhD Student Political Science - UCLA
> Web: felipenunes.bol.ucla.edu
>
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>
> ______________________________________________
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>
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