From: Sean Davis > > On 3/23/06 5:52 AM, "Noam Friedman" <[EMAIL PROTECTED]> wrote: > > > Hi all! > > > > > > I was wondering if you can help me with a little sampling issue I'm > > having in R. > > > > I have a database with 100 observations. > > I need to sample n=9 sample size, 200 times (i.e. get 200 > samples of > > size 9). N (pop. size) =100 > > > > Each sample can't contain the same observation more than one time > > (i.e. the program needs to check if the obs. has already > been sampled > > into the sample - it it has, it should put it back and sample again > > another obs.) > > > > obviously I need to do this with replacement. > > > > Then, I need to draw (I think the best is with a histogram) the > > distribution of the mean of each os the 200 samples. > > > > I guess I need to do a loop for the 'sample' function in R. > > That sounds correct. > > > I could really use your help. > > x <- rnorm(100) > meanvec <- vector() > for (j in 1:200) { > y <- sample(x,9) > meanvec[j] <- mean(y) > } > hist(meanvec)
If the samples are not needed beyond the calculations Noam mentioned, then this might save some memory: samp.means <- replicate(200, mean(sample(x, 9))) hist(samp.means) Andy > If this example code doesn't get you started, then you will > probably need to be more specific about where you are getting stuck. > > Sean > > ______________________________________________ > 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 > > ______________________________________________ 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