Re: 3D plot with range restricted to non-rectangular region
- To: mathgroup at smc.vnet.net
- Subject: [mg66133] Re: [mg66097] 3D plot with range restricted to non-rectangular region
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Sun, 30 Apr 2006 04:21:58 -0400 (EDT)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
h[x_,y_,z_]:=Log[x]+Log[y]+Log[z];
h2[x_,y_]:=h[x,y,1-x-y];
Off[Plot3D::gval];
Plot3D[h2[x, y], {x, 10^-15, 1}, {y,10^-15, 1}];
Off[ContourGraphics::ctpnt];
ContourPlot[h2[x, y], {x, 10^-15, 1}, {y,10^-15, 1}];
Bob Hanlon
---- David Sanders <dpsanders at gmail.com> wrote:
> Hi,
>
> I want to plot a function whose range is naturally restricted to a
> non-rectangular region:
>
> h[x_, y_, z_] := Log[x] + Log[y] + Log[z]
>
> h2[x_, y_] := h[x, y, 1 - x - y]
>
> Only the region {(x,y): 0<x<1; 0<y<1-x} is allowed.
>
> If I try the naive
> Plot3D[h2[x, y], {x, 0, 1}, {y, 0, 1}]
>
> then I get error messages of the type:
>
> Plot3D::plnc: h2[x, y] is neither a machine-size real number at {x,
> y}={0.5, \
> 0.5} nor a list of a real number and a valid color directive
>
> But then it plots the graph anyway.
>
> I also need contour plots of functions like this.
>
> Is there a proper way of avoiding these error messages, like making it
> ignore points whenever they contain an illegal operation (here, Log of
> a negative number)?
>
> Thanks,
> David.
>