First of all, your subscripting is wrong. The first index is for row, and the second for column. Thus large[i,] refers to the i-th row of large, rather than the i-th column. Also, the code as you provided contain syntax error.
Try: set.seed(311) ## Always a good idea to set seed for simulation! large <- matrix(rnorm(1000*1000), 1000, 1000) small <- matrix(rnorm(100*1000), 100, 1000) var.large <- apply(large, 2, var) ## Apply the var function to each column var.small <- apply(small, 2, var) The result looks like: > summary(var.large); summary(var.small) Min. 1st Qu. Median Mean 3rd Qu. Max. 0.8617 0.9705 1.0010 1.0020 1.0320 1.1520 Min. 1st Qu. Median Mean 3rd Qu. Max. 0.5846 0.9021 0.9948 0.9990 1.0850 1.5360 as expected: The mean is about the same, but the spread is much smaller for larger sample size. This sort of things can be computed exactly using basic math stat, BTW. Andy > -----Original Message----- > From: Padmanabhan, Sudharsha [mailto:[EMAIL PROTECTED] > Sent: Tuesday, August 19, 2003 1:43 PM > To: [EMAIL PROTECTED] > Subject: [R] Variance Computing- - HELP!!!!!!!!!!!!!!!!!! > > > > Hello, > > I am running a few simulations for clinical trial anlysis. I > want some help > regarding the following. > > We know trhat as the sample size increases, the variance > should decrease, but > I am getting some unexpected results. SO I ran a code (shown > below) to check > the validity of this. > > large<-array(1,c(1000,1000)) > small<-array(1,c(100,1000)) > for(i in 1:1000){large[i,]<-rnorm(1000,0,3)} > for(i in 1:1000){small[i,]<-rnorm(100,0,3)}} > yy<-array(1,100) > for(i in 1:100){yy[i]<-var(small[i,])} > y1y<-array(1,1000) > for(i in 1:1000){y1y[i]<-var(large[i,])} > mean(yy);mean(y1y); > [1] 8.944 > [1] 9.098 > > > This shows that on an average,for 1000 such samples of 1000 > Normal numbers, > the variance is higher than that of a 100 samples of 1000 > random numbers. > > Why is this so? > > > Can someone please help me out???? > > Thanks. > > Regards > > ~S. > > ______________________________________________ > [EMAIL PROTECTED] mailing list > https://www.stat.math.ethz.ch/mailman/listinfo> /r-help > ------------------------------------------------------------------------------ Notice: This e-mail message, together with any attachments, contains information of Merck & Co., Inc. (Whitehouse Station, New Jersey, USA), and/or its affiliates (which may be known outside the United States as Merck Frosst, Merck Sharp & Dohme or MSD) that may be confidential, proprietary copyrighted and/or legally privileged, and is intended solely for the use of the individual or entity named on this message. If you are not the intended recipient, and have received this message in error, please immediately return this by e-mail and then delete it. ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help