From: Camarda, Carlo Giovanni <Camarda_at_demogr.mpg.de>

Date: Tue 31 Jan 2006 - 02:29:38 EST

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 Received on Tue Jan 31 02:48:24 2006

Date: Tue 31 Jan 2006 - 02:29:38 EST

Dear R-users,

I'm struggling in R in order to "squeeze" a matrix without using a
for-loop.

Although my case is a bit more complex, the following example should
help you to understand what I would like to do, but without the slow
for-loop.

Thanks in advance,

Carlo Giovanni Camarda

A <- matrix(1:54, ncol=6) # my original matrix
A.new <- matrix(nrow=3, ncol=6) # a new matrix which I'll fill
# for-loop

for(i in 1:nrow(A.new)){

B <- A[i:(i+2), ] # selecting the rows C <- apply(B,2,sum) # summing by columns A.new[i,] <- C # inserting in the new matrix}

+++++

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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 Received on Tue Jan 31 02:48:24 2006

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