Hello David and Dennis,
thank you two for your replies. You not only helped me solve my problem,
but also helper me to understand my problem better.
Here is my -now working- code:
x<-y<-seq(-4,4,len=40)
g<-function(a,b) {
dmvnorm(x=cbind(a,b),sigma=matrix(c(4,2,2,3), ncol = 2))
}
z<-outer(x,y,g)
persp(x,y,z)
Thank you a lot!
Severin