From: Robin Hankin <r.hankin_at_soc.soton.ac.uk>

Date: Tue 26 Apr 2005 - 17:45:11 EST

Date: Tue 26 Apr 2005 - 17:45:11 EST

try this (but there must be a better way!)

stratified.select <- function(A,J){

out <- sapply(J,function(i){sample(A[,,i],1)})
attributes(out) <- attributes(J)

return(out)

}

A <- array(letters[1:12],c(2,2,3))

J <- matrix(c(1,2,3,3),2,2)

[,1] [,2]

[1,] "b" "i"

[2,] "g" "k"

R> stratified.select(A,J)

[,1] [,2]

[1,] "d" "j"

[2,] "f" "l"

R>

best wishes

Robin

On Apr 26, 2005, at 05:16 am, juhana vartiainen wrote:

> Hi all

*>
**> Suppose I have a dim=c(2,2,3) matrix A, say:
**>
**> A[,,1]=
**> a b
**> c d
**>
**> A[,,2]=
**> e f
**> g h
**>
**> A[,,3]=
**> i j
**> k l
**>
**> Suppose that I want to create a 2x2 matrix X, which picks elements
**> from the above-mentioned submatrices according to an index matrix J
**> referring to the "depth" dimension:
**> J=
**> 1 3
**> 2 3
**>
**> In other words, I want X to be
**> X=
**> a j
**> g l
**>
**> since the matrix J says that the (1,1)-element should be picked from
**> A[,,1], the (1,2)-element should be picked from A[,,3], etc.
**>
**> I have A and I have J. Is there an expression in A and J that creates
**> X?
**>
**> Thanks
**>
**> Juhana
**>
**> juhana@fief.se
**>
**> --
**> Juhana Vartiainen
**>
**> docent in economics
**> Director, FIEF (Trade Union Foundation for Economic Research,
**> Stockholm), http://www.fief.se
**> gsm +46 70 360 9915
**> office +46 8 696 9915
**> email juhana@fief.se
**> homepage http://www.fief.se/staff/Juhana/index.html
**>
**> ______________________________________________
**> R-help@stat.math.ethz.ch mailing list
**> https://stat.ethz.ch/mailman/listinfo/r-help
**> PLEASE do read the posting guide!
**> http://www.R-project.org/posting-guide.html
**>
**>
*

-- Robin Hankin Uncertainty Analyst Southampton Oceanography Centre European Way, Southampton SO14 3ZH, UK tel 023-8059-7743 ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.htmlReceived on Tue Apr 26 17:51:09 2005

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