[R] problem with nested loops

From: Jens Oldeland <oldeland_at_gmx.de>
Date: Wed, 30 Jul 2008 09:49:03 +0200


Dear all,

I have a problem with constructing a nested loop.

I have two matrices:

pnr:
800 rows 14 columns

where rows are 40x20 meaning that 40 rows belong to one of twenty objects in the matrix pnr

mvp:
20 rows and 14 columns

I want to:
calculate a distance value with the first 40 rows of pnr but 20times with the 1st row of mvp

then the next 40 rows of pnr and 20times with the second row of mvp and so on. in total 20 times.

i tried with:

> dim(p)

[1] 800 14
> dim(mvp)

[1] 20 14

specdist <-matrix(NA,nrow=40,ncol=20)

for (j in 1:40){

   for(i in 1:20){
specdist[j,i]<-sqrt((pnr[i,1]-mvp[i,1])^2+(pnr[i,2]-mvp[i,2])^2)+....+(pnr[i,14]-mvp[i,14])^2)) }
}

but it only repeats from 1:40 and does not step from 41 to 80; from 81 to 40 etc. certainly there is a "if" "else" "next" "step??" or "while" missing, but I never implemented one of those. :(

I would be very grateful for any help!
thank you

Jens



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