Hi!
maybe because sample variance has N-1 at the denominator (say degrees of freedom)? so all.equal((sum(x^2) - 100*mean(x)^2)/99, var(x)) ## TRUE but (sum(x^2) - 100*mean(x)^2)/100 # == your value Stef On Wed, Nov 28, 2007 at 09:56:58AM +0100, Tine wrote: <Tine>Hi! <Tine> <Tine>Let us define random variable: <Tine> > x = seq(0,1,length=100) <Tine> <Tine>If we calculate variance following definition E[(x-E(x))^2] we get: <Tine> > mean( (x - mean(x))^2 ) # == mean(x^2) - mean(x)^2 <Tine>0.08501684 <Tine> <Tine>And if we use internal R function var: <Tine> > var(x) <Tine>0.08587559 <Tine> <Tine>Can anyone tells me why the difference? <Tine> <Tine>______________________________________________ <Tine>R-help@r-project.org mailing list <Tine>https://stat.ethz.ch/mailman/listinfo/r-help <Tine>PLEASE do read the posting guide http://www.R-project.org/posting-guide.html <Tine>and provide commented, minimal, self-contained, reproducible code. ______________________________________________ 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.
