> From: "Volker Bahn" <lochapoka@web.de>
> Date: Mon, 13 Dec 2004 09:53:37 -0500
>
> I want to create a 3D persp plot that does not cover a square. Is that
> possible? I calculated predictions from a model for certain parameter
> combinations of R (growth rate) and death (death rate). However, certain
> parameter combinations do not lead to results in the model so that I cannot
> fill a square matrix with parameter combinations. The death rate cannot be
> higher than the growth rate leading to a diagonal cut off in the possible
> combinations. When I create a persp() plot from this, I get non-sense
> extrapolations into the empty parameter space. Is it possible to turn this
> off or cut it off? I searched help files and s-news archives but found
> nothing. The data is posted below (Istd is the model output).
>
?persp says:
z
matrix of size length(x) by length(y) giving the surface height
at grid points, i.e., z[i,j] is evaluated at x[i], y[j]. The
rows of z are indexed by x, and the columns by y. Missing
values ( NAs) are allowed, but should generally not occur in
the convex hull of the non-missing values.
Note the bit about missing values.
Ray Brownrigg
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