MathGroup Archive 2002

[Date Index] [Thread Index] [Author Index]

Search the Archive

RE: plotting with boundary conditions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg34520] RE: [mg34482] plotting with boundary conditions
  • From: "Annetts, Dave (E&M, North Ryde)" <David.Annetts at csiro.au>
  • Date: Fri, 24 May 2002 02:42:39 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Raj,
to plot a surface 
>   f(a,b) = a^2-2*c(a,b)+b^2; given the boundary conditions c(a,b)< ab
> 
>   Here c(a,b) is another function of (a,b) given by
>   c(a,b) = 0.1*(a-1)^2+0.1*(b-1)^2-0.01
> 
> Is there a direct command to set these boundary 
> conditions...?? If i give 
> 
> f[a_, b_] := If[c[a, b] < a*b, a^2 + b^2 - 2*c[a, b],];
> 
> Plot3D[f[a, b], {a, 0, 2}, {b, 0, 2}, AxesLabel -> {"a", "b", "f"}, 
>   ViewPoint -> {2, 2, 2}]
> 
> I get error messages for the values of a and b for which 
> f(a,b) doesnot exist.
> 
> Can anybody please tell me how i can get this plot?

After defining your function c, it works fine ...

c[a_, b_] := 0.1*(a-1)^2+0.1*(b-1)^2-0.01

f[a_,b_]:=If[c[a,b]<a*b,a^2+b^2-2*c[a,b],Null];
Plot3D[f[a,b],{a,0,2},{b,0,2},AxesLabel\[Rule]{"a","b","f"},
  ViewPoint\[Rule]{2,2,2}];

You can supress the warnings by setting 
Off[Plot3D::plnc];
Off[Plot3D::gval];

Regards,

Dave.
--------------------------------------------------------
  Dr. David Annetts             EM Modelling Analyst
  Tel: (+612) 9490 5416         CSIRO DEM, North Ryde
  Fax: (+612) 9490 5467         David.Annetts at csiro.au
                 Include "usual_disclaimers"
--------------------------------------------------------


  • Prev by Date: 4.1 no graphics in HP-UX 10.20 ?
  • Next by Date: Re: plotting with boundary conditions
  • Previous by thread: Re: plotting with boundary conditions
  • Next by thread: Re: plotting with boundary conditions