[R] sampling vectors

[ecatchpole]

Eric,

If you want samples of size 3 from 0:50, with sum==50, this seems to do 
the job (with apologies to those who really know how to program in R):

tot <- 50
ii <- 0
aa <- list()
for(i in 0:tot){
    for(j in 0:(tot-i)){
       k <- tot-i-j
       ii <- ii+1
       aa[[ii]] <- list(i=i,j=j,k=k)
    }
}

aa[sample(ii, 4)] # for a sample of 4.

If you want a sample of size n from x[1],...x[N], such that the sample 
sum is T, then that is much trickier!

Ted.

On 04/10/05 07:31,  Eric Pante wrote,:
> Hello Listers,
> 
> I am trying to sample a vector to create a new one of sample length, 
> witha  sum equal to the sum of the initial vector:
> 
> initial = 10, 30, 10 (sum=50)
> sample example = 5, 35, 10 (sum=50) or 25, 15, 10  (sum=50), etc ...
> 
> My problem is to control the sum, so it stays constant.
> Any suggestions would be very helpful !
> 
> Thank you in advance,
> Eric
> 
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-- 
Dr E.A. Catchpole
Visiting Fellow
Univ of New South Wales at ADFA, Canberra, Australia
and University of Kent, Canterbury, England
- www.ma.adfa.edu.au/~eac
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