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MathGroup Archive 1998

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Re: Restrict domain of Plot3D[]?

  • To: mathgroup at
  • Subject: [mg13115] Re: Restrict domain of Plot3D[]?
  • From: Paul Abbott <paul at>
  • Date: Tue, 7 Jul 1998 03:44:18 -0400
  • Organization: University of Western Australia
  • References: <6nn9u1$>
  • Sender: owner-wri-mathgroup at

robpeterson at wrote:
> I'm plotting f[x,y] where x+y<1.  Presently I'm getting this done by
> Plot3D[ If[ x+y<1 ], f[x,y], 0], {x,0,1}, {y,0,1}]
> Here, the forbidden area where x+y>1 transitions down to the 0 level.
> Things are working OK but the transition looks lousy.
> Is there some way to just stop the plotting at the boundary where x+y
> become 1?  Or, some other method ?
> Any clues will be greatly appreciated.

An answer for this appeared in The Mathematica Journal 5(1):15. Change
variables and reparametrise y:

	ParametricPlot3D[{x,u (1-x),f[x,u (1-x)]},{x,0,1},{u,0,1}];

Here y -> u (1-x) and u:[0,1].

Paul Abbott                                   Phone: +61-8-9380-2734
Department of Physics                           Fax: +61-8-9380-1014
The University of Western Australia            Nedlands WA  6907       
mailto:paul at  AUSTRALIA                   

            God IS a weakly left-handed dice player

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