[EMAIL PROTECTED] wrote: > I'm having trouble with the standard deviation distribution > as shown on http://mathworld.wolfram.com/StandardDeviationDistribution.html . > (Eric Weisstein references Kenney and Keeping 1951, which I can't check.) > > I believe the graphs they show, but when I code the function in R, according > to the listed formula, > I get very different graphs. > > Would someone please point out my error or tell me where it's already > implemented in R? > > Here is my version: > >> sddist >> > function(s,n) { > sig2 <- n*s*s/(n-1) > 2*(n/(2*sig2))^((n-1)/2) / gamma((n-1)/2) * exp(-n*s*s/(2*sig2)) * s^(n-2) > } > > Your initial factor looks a lot different from theirs. I think you believed your variable name (i.e. sig2 is sigma^2), but didn't define it that way.
Duncan Murdoch > Version 2.3.1 (2006-06-01) on Windows XP SP2 > > Thanks for any help. > > David L. Reiner > Rho Trading Securities, LLC > Chicago IL 60605 > 312-362-4963 > > ______________________________________________ > 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