Re: [R] empirical null distribution

From: Duncan Murdoch <>
Date: Tue, 29 Apr 2008 08:45:27 -0400

On 29/04/2008 8:09 AM, mad_bassie wrote:
> I'm using F-distributions :)
> I allready found some things...I could plot the qqplot as you say and that
> gives me clear results.
> Allthough I still want a clear graphic and I 'll explain it as good as I
> can...
> I plotted 2 graphics
> plot(density(rf(10000,2,49)))
> plot(density(disttest))
> (the "disttest" is a distribution i simulated myself like this:
> for(i in 1:100){
> X<-rnorm(50,20,4)
> Y<-rnorm(50,20,5)
> Z<-rnorm(50,20,4)
> vector<-c (X, Y, Z)
> vector2<-rep(c('X','Y','Z'),c(50,50,50))
> data1<-data.frame(waarde=vector, soort = vector2)
> library(mvtnorm)
> library(multcomp)
> data1$soort<-as.factor(data1$soort)
> disttest<-c(disttest,summary(aov(waarde~soort,data=data1))[[1]][1,4])
> }
> (I want to compare the theroretical F-distribution with a distribution where
> the variances are not equal...)
> Thos are 2 fine plots but I just can't figure out how to put them together
> in one this possible in would make things much clearer
> because the window setting are not really equal wich makes it difficult to
> compare...

You'd be better off comparing p-values than densities, but you can do what you're trying by using lines(density(disttest)) instead of calling plot() again.

Duncan Murdoch mailing list PLEASE do read the posting guide and provide commented, minimal, self-contained, reproducible code. Received on Tue 29 Apr 2008 - 13:06:22 GMT

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