[R] what am I missing

[Gabor Grothendieck]

Its a FAQ:

http://hermes.sdu.dk/Rdoc/faq.html#Why%20does%20outer()%20behave%20strangely%20with%20my%20function%3f

On 9/10/07, Jan de Leeuw <deleeuw at stat.ucla.edu> wrote:
> x<-seq(-1,1,length=10)
> y<-seq(-1,1,length=10)
> a<-matrix(c(1,2,2,1),2,2)
> b<-matrix(c(2,1,1,2),2,2)
>
> fv<-function(x,y) {
>        m<-x*a+y*b
>        t<-m[1,1]+m[2,2]; d<-m[1,1]*m[2,2]-m[1,2]^2
>        return((t-sqrt(t^2-4*d))/2)
> }
>
> gv<-function(x,y) {
>        t<-x*(a[1,1]+a[2,2])+y*(b[1,1]+b[2,2])
>        d<-(x*a[1,1]+y*b[1,1])*(x*a[2,2]+y*b[2,2])-(x*a[1,2]+y*b[1,2])^2
>        return((t-sqrt(t^2-4*d))/2)
> }
>
>
> now outer(x,y,gv) works as expected, outer(x,y,fv) bombs. But
>
> z<-matrix(0,10,10); for (i in 1:10) for (j in 1:10) z[i,j]<-fv(x[i],y
> [j])
>
> works fine. Must be something in outer().
>
> ==========================================================
> Jan de Leeuw, 11667 Steinhoff Rd, Frazier Park, CA 93225, 661-245-1725
> .mac: jdeleeuw ++++++  aim: deleeuwjan ++++++ skype: j_deleeuw
> homepages: http://www.cuddyvalley.org and http://gifi.stat.ucla.edu
> ==========================================================
>                A bath when you're born,
>           a bath when you die,
>                how stupid.          (Issa 1763-1827)
>
>
>
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at 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
> and provide commented, minimal, self-contained, reproducible code.
>