[R] problem with nested loops
Jens Oldeland
oldeland at gmx.de
Wed Jul 30 09:49:03 CEST 2008
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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