I tried your sample code, and a few other variations, and got 0 for all of them, running R 1.8.1 on a Windows machine
Not only do I get 0 on R 1.8.1 on Unix (linux, RH8), I get _exactly_ 0. I thought this was going to be a simple arithmetic precision problem, but this test script shows the answers to be exactly zero:
zertest <- function(q){
if( q != 0 ){
theCall <- deparse(substitute(q))
cat(paste("failed",theCall,' : got ',q,'\n',sep=' '))
}
}# these fail, as expected: zertest(sd(c(1,2,3))) zertest(sd(c(rep(0.01,12),0.00000001)))
# these pass as zero: zertest(sd(rep(0.01, 13))) #1.805557e-18 zertest(sd(rep(0.001, 13))) #4.513894e-19 zertest(sd(rep(0.00001, 13))) #0 zertest(sd(rep(0.00000001,13))) #0
Might be a compiler/config funny. Andreas: what 'UNIX' is this? Did you compile R yourself? Did you run 'make check'?
Baz
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