\begin{Schunk}
\begin{Sinput}
 x1 <- rnorm(100); x2 <- rpois(100,lambda=4) 
 logist <- function(x1,x2){
  y <- 1/(1 + exp((-1)*(-3 + 0.6*x1 + .5*x2))) } 
 par(bg = "white") 
 x1r <- range(x1) ; x1seq <- seq(x1r[1], x1r[2], length = 30)
 x2r <- range(x2) ; x2seq <- seq(x2r[1], x2r[2], length=30)
 z <- outer(x1seq, x2seq, logist)
 persp(x=x1seq,y=x2seq, z=z, theta=-30, zlim=c(-0.2,1.2))
\end{Sinput}
\end{Schunk}
