Re: Limiting range of variables when defining funxtions

• To: mathgroup at smc.vnet.net
• Subject: [mg74700] Re: [mg74676] Limiting range of variables when defining funxtions
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Sun, 1 Apr 2007 04:15:08 -0400 (EDT)

```Off[Plot3D::plnc,Plot3D::gval];

Clear[test];
test[x_/;0<=x<=1,y_/;0<=y<=1-x]:=x+y;

Plot3D[test[x,y],{x,-0.1,1.1},{y,-0.1,1.1}];

Clear[test];
test[x_,y_]:=(x+y)*Boole[0<=x<=1&&0<=y<=1-x];

Plot3D[test[x,y],{x,-0.1,1.1},{y,-0.1,1.1}];

Clear[test];
test[x_,y_]:=Piecewise[
{{x+y,0<=x<=1&&0<=y<=1-x}}];

Plot3D[test[x,y],{x,-0.1,1.1},{y,-0.1,1.1}];

Bob Hanlon

---- Michelasso <qzerty at gmail.com> wrote:
> Hello everybody,
> my problem is that I would like to plot a 3d graphic of a function of
> two variables, restricted to domain D={(x,y): x>= 0, y>=0, y <= 1-x}.
>
> I thought to define the function in this way:
> test[x_,y_/; y <= 1-x]:= x+y
>
> but this seems not to work, while it works for functions of one
> variable, i.e.:
> test2[x_/; x<= 1]:= 3x
>
> So, am I doing some syntax error, or is there some other kind of
> problems with my definition?
>

```

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