[R] split-apply question
jim holtman
jholtman at gmail.com
Fri Oct 2 11:24:42 CEST 2009
try this:
> x <- read.table(textConnection("x1 x2 x3
+ A 1 1.5
+ B 2 0.9
+ B 3 2.7
+ C 7 1.8
+ D 7 1.3"), header=TRUE)
> closeAllConnections()
> do.call(rbind, lapply(split(seq(nrow(x)), x$x1), function(.row){
+ x[.row[which.min(x$x2[.row])],]
+ }))
x1 x2 x3
A A 1 1.5
B B 2 0.9
C C 7 1.8
D D 7 1.3
>
On Thu, Oct 1, 2009 at 11:43 PM, Kavitha Venkatesan
<kavitha.venkatesan at gmail.com> wrote:
> Hi,
>
> I have a data frame that looks like this:
>
>>x
>
> x1 x2 x3
> A 1 1.5
> B 2 0.9
> B 3 2.7
> C 7 1.8
> D 7 1.3
>
> I want to "group" by the x1 column and in the case of multiple x$x1 values
> (e.g., "B")d, return rows that have the smallest values of x2. In the case
> of rows with only one value of x1 (e.g., "A"), return the row as is. How can
> I do that? For example, in the above case, the output I want would be:
>
> x1 x2 x3
> A 1 1.5
> B 2 0.9
> C 7 1.8
> D 7 1.3
>
>
> Thanks!
>
> [[alternative HTML version deleted]]
>
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--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
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