[R] Matrix oriented computing

[Achim Zeileis]

On Fri, 26 Aug 2005 14:44:10 +0200 Sigbert Klinke wrote:

> Hi,
> 
> I want to compute the quantiles of Chi^2 distributions with different 
> degrees of freedom like
> 
> x<-cbind(0.005, 0.010, 0.025, 0.05, 0.1, 0.5, 0.9, 0.95, 0.975, 0.99,
> 0.995) df<-rbind(1:100)
> m<-qchisq(x,df)
> 
> and hoped to get back  a  length(df) times length(x)  matrix with the 
> quantiles. Since this does not work, I use
> 
> x<-c(0.005, 0.010, 0.025, 0.05, 0.1, 0.5, 0.9, 0.95, 0.975, 0.99,
> 0.995) df<-c(1:100)
> m<-qchisq(x,df[1])
> for (i in 2:length(df)) {
>   m<-rbind(m,qchisq(x,df[i]))
> }
> dim(m)<-c(length(df),length(x))
> 
> Is there a way to avoid the for loop ?

You could use sapply():
  m <- sapply(x, function(x) qchisq(x, df))
hth,
Z

> Thanks Sigbert
> 
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