Plot 3D plane (true regression surface)

Question

I\'m trying to simulate some data (x1 and x2 - my explanatory variables), calculate y using a specified function + random noise and plot the resulting observations AND the t

Answer 1

Apologies: ( I didn't read the question very carefllly and now see that I rushed into estimation when you wanted to plot the Truth.)

Here's an approach to estimation followed by surface plotting using loess:

mod2 <- loess(y~x1+x2)
grd<- data.frame(x1=seq(range(x1)[1],range(x1)[2],len=20), 
                 x2=seq(range(x2)[1],range(x2)[2],len=20))
grd$pred <- predict(mod2, newdata=grd)
grd <- grd[order(grd$x1,grd$x2),]
x1 <- unique(grd$x1)
x2 <- unique(grd$x2)   # shouldn't have used y
surface3d(x1, x2, z=matrix(grd$pred,length(x1),length(x2)) )