[R] split-apply question

[jim holtman]

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

What is the problem that you are trying to solve?