# Surface Example
# R script to create perspective and contour plots.

f = function(x, y) {
   return(13 + 2*x + 3*y - 2.5*x^2 - 3.5*y^2 + 2*x*y)
}

f(2, 3)
x = seq(-1, 1, 0.1)
y = seq(-1, 1, 0.1)
z = outer(x, y, f)

pdf("contour-plots.pdf")
persp(x, y, z, theta=30, phi=30, xlab="x", ylab="y", zlab="z",
   main="3 Dimensional Perspective Plot")
contour(x, y, z, nlevels=10, xlab="x", ylab="y",
   main="Contour Plot")
dev.off( )