Hi Dan, I just tried your code with long vectors, and the sampling stops to be random. Do you see any reason why this is ?
examples: ex = c(30,13,9,8,7,7,7,6,6,5,2,2,2,1,1,1,1,1,1,1,1,1,1,1,1,1) > vectorSample(ex) [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 3 1 7 6 [24] 4 2 75 > vectorSample(ex) [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 1 2 11 [24] 7 8 67 > > vectorSample(ex) [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 [24] 1 6 87 > vectorSample(ex) [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 1 1 1 2 3 [24] 1 4 85 > vectorSample(ex) [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 19 [24] 16 42 18 > vectorSample(ex) [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 3 5 4 4 17 [24] 2 53 10 > vectorSample(ex) [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 3 5 [24] 3 11 74 > vectorSample(ex) [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 3 3 1 2 3 [24] 21 23 43 > vectorSample(ex) [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 5 9 [24] 18 20 44 > vectorSample(ex) [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 3 6 14 [24] 8 6 59 On Oct 4, 2005, at 12:02 PM, Daniel Nordlund wrote: >> -----Original Message----- >> From: [EMAIL PROTECTED] >> [mailto:[EMAIL PROTECTED] >> On Behalf Of ecatchpole >> Sent: Monday, October 03, 2005 11:57 PM >> To: Eric Pante >> Cc: r-help@stat.math.ethz.ch >> Subject: Re: [R] sampling vectors >> >> 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 >>> > > Eric, > > Here is another solution, which allows vectors of different lengths > and sums. > > vectorSample <- function(vec) { > tot<-sum(vec) > Len<-length(vec) > v < -rep(0,Len) > for(i in Len:2) { > UL <- tot - sum(v) - i + 1 > v[i]<-sample(1:UL,1) > } > v[1] <- tot - sum(v) > v > } > > vectorSample( c(10,30,10) ) > > Hope this helps, > > Dan Nordlund > Bothell, WA > > > > Eric Pante --------------------------------------------------------------- Graduate Student in Marine Biology Grice Marine Laboratory 205 Fort Johnson Road, Charleston SC 29412 --------------------------------------------------------------- "On ne force pas la curiosite, on l'eveille ..." Daniel Pennac [[alternative text/enriched version deleted]] ______________________________________________ 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
