[R] rgl 3d surface

[S Ellison]

> -----Original Message-----
> > I compute its regression surface doing polynomical regression (fit)
> > ...
> > fit <- lm(z ~ poly(x,2) + poly(y,2))
> >
.....
> > So I want to repressent the surface
.... 
> > How could I do it? Any idea??
> 
> You need to write a function f of x and y that produces the fitted values.  I
> haven't checked, but I'd assume it needs to take vector inputs and produce a
> vector of responses.  

Perhaps worth noting that since the fit was produced by lm(), predict() will generate the surface values without a separate function.

For example, if we said something like [sorry, not yet checked]

xvals <- seq(-35, -15, 0.5)
yvals <- seq(-35, -15, 0.5)
new.data <- data.frame(x=rep(xvals, each=length(yvals)), y=rep(yvals, length(xvals) )
new.data$z <- predict(fit, newdata=new.data)
#This should generate the predicted surface

#Then:
with(new.data, persp3d(x, y, z)) 

#ought to do the job.



> Then
> 
> 
> persp3d(f)
> 
> will draw the surface.  See ?persp3d.function for details on setting the x and y
> ranges, etc.
> 
> Duncan Murdoch
> 
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