Dan Nordlund, Dan (DSHS/RDA) wrote: > >> -----Original Message----- >> From: r-help-bounces@ [mailto:r-help-bounces@r- >> project.org] On Behalf Of SarahJoyes >> Sent: Tuesday, November 08, 2011 5:57 AM >> To: r-help@ >> Subject: Re: [R] Sampling with conditions >> >> That is exactly what I want, and it's so simple! >> Thanks so much! >> > > Sarah, > > I want to point out that my post was qualified by "something like". I am > not sure it is exactly what you want. Since you didn't quote my post, let > me show my suggestion and then express my concern. > > n <- matrix(0,nrow=5, ncol=10) > repeat{ > c1 <- sample(0:10, 4, replace=TRUE) > if(sum(c1) <= 10) break > } > n[,1] <- c(c1,10-sum(c1)) > n > > This nominally meets your criteria, but it will tend to result in larger > digits being under-represented. For example, you unlikely to get a result > like c(0,8,0,0,2) or (9,0,0,1,0). > > That may be OK for your purposes, but I wanted to point it out. > > You could use "something like" > > n <- matrix(0,nrow=5, ncol=10) > c1 <- rep(0,4) > for(i in 1:4){ > upper <- 10-sum(c1) > c1[i] <- sample(0:upper, 1, replace=TRUE) > if(sum(c1) == 10) break > } > n[,1] <- c(c1,10-sum(c1)) > n > > if that would suit your purposes better. > > > Good luck, > > Dan > > Daniel J. Nordlund > Washington State Department of Social and Health Services > Planning, Performance, and Accountability > Research and Data Analysis Division > Olympia, WA 98504-5204 > > > ______________________________________________ > R-help@ mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >
Perhaps a little bit of context may be helpful, I am trying to figure out the ideal age structure for a population of ten individuals that would yield the best overall survival rate given that each age group has different survivorbility and different reproductive rates. So yes, having a bias for smaller numbers would be a problem. The only other problem that I see with your revised code is that there will be a bias towards having higher numbers in the first age group or first row of the column... The other idea I was playing with was to create a series of ifelse statements for each row of the column... Something like: n<-matrix(0,nr=5,ncol=10) n[1,1]<-sample(0:10,1) n[2,1]<-ifelse(n[1,1]=10,0,sample(0:10,1)) n[3,1]<-ifelse(sum(n[i,1])>10,0,sample(0:10,1)) etc... I still think that might be biased towards high numbers in the first rows though... hmmm SJ -- View this message in context: http://r.789695.n4.nabble.com/Sampling-with-conditions-tp4014036p4017351.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
