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MathGroup Archive 2006

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Re: General--IF condition in Plot3D

  • To: mathgroup at
  • Subject: [mg69014] Re: General--IF condition in Plot3D
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at>
  • Date: Sat, 26 Aug 2006 04:40:04 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <ecoojc$2s6$>
  • Sender: owner-wri-mathgroup at

madhukarrapaka at wrote:
> How to use a IF condition in Plot3D??
> For example:
> I have "I" values caluclated by I=P/2*Pi*r*L .; where P=10.3,L=0.45,r=dist. 
> So if i want to plot "I" when "r<x", how to do it??
> (Here i am giving my procedure thru which i am getting a Plot with some warning)
> r[x_,y_]:=Sqrt[x^2+y^2];
> I[x_,y_]:=P/2*Pi*r[x_,y_]*L
> Plot3D[If[r[x,y]<=0.082,I[x,y]],{x,-0.082,0.082},{y,-0.082,0.082}]
 > [...]
> Is there anything wrong in the syntax or range specification.

The following works:

r[x_, y_] := Sqrt[x^2 + y^2];
i[x_, y_] := (P/2)*Pi*r[x, y]*L
Plot3D[Boole[r[x, y] <= 0.082]*i[x, y] /.
  {P -> 10.3, L -> 0.45}, {x, -0.082, 0.082},
  {y, -0.082, 0.082}];


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