transform_xy error: value NIL is not of type DOUBLE-FLOAT

Hi Ray,

I initially discovered the problem with a more complex (and important to 
me) function involving sqrts of cos and sin, and I subsequently 
simplified the problem down to the simplest function I could find that 
reproduced the bug.

The bug has been filed as #2579.

Cheers,

Adrian

On 5/23/13 2:12 PM, Raymond Toy wrote:
>>>>>> "Adrian" == Adrian Brown <abrown at seti.org> writes:
>      Adrian> Hi all,
>      Adrian> I was wondering if anyone can help me make this work?
>
>      Adrian> wxplot3d([r,theta,sqrt(sin(theta))],[r,0,1],[theta,0,2*%pi],
>      Adrian> [gnuplot_pm3d,true],
>      Adrian> [gnuplot_preamble, "set pm3d
>      Adrian> map"],[grid,1,1],[transform_xy,make_transform([r,theta,z],r*cos(theta),r*sin(theta),z)])$
>
>      Adrian> The error I get is:
>
>      Adrian> Maxima encountered a Lisp error:
>      Adrian> The value NIL is not of type DOUBLE-FLOAT.
>
> Maxima should definitely do a better job here than signal a lisp
> error.  Could you file a bug about that with this example?
>
> However, what is it are you trying to plot with sqrt(sin(theta))?
> Since sin(theta) <= 0 for %pi <= theta <= 2*%pi, plot3d probably gets
> an error from taking the sqrt of a negative number and not knowing how
> to deal with that.
>
> Ray
>
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