Re: newbie problem with NIntegrate
- To: mathgroup at smc.vnet.net
- Subject: [mg49811] Re: newbie problem with NIntegrate
- From: Paul Abbott <paul at physics.uwa.edu.au>
- Date: Sun, 1 Aug 2004 18:48:43 -0400 (EDT)
- Organization: The University of Western Australia
- References: <cei8o5$2he$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
In article <cei8o5$2he$1 at smc.vnet.net>,
"Xiaoxun" <dbjunxiao at hotmail.com> wrote:
> Please advices:
>
> Geom = (200 >=x>= 100 && 50 >= y >= -50 && -20 <= z <= 20);
> gr[x_, y_, z_] := 2 /; Geom;
> gr[x_, y_, z_] := 0 /; ! (Geom);
> N[Integrate[gr[x, y, z], {x, 0, 300}, {y, -100, 100}, {z, -30, 30}]
> This gives a result of 799995.
> However, if changing the x range to {x,0,600} results 799993.
> and {x,0,900} results 0;
>
> So what could we do to ensure the right answer?
In version 5.0, load
<< Calculus`Integration`
and us Boole:
Integrate[2 Boole[200 >=x>= 100 && 50 >= y >= -50 && -20 <= z <= 20],
{x, 0, 300}, {y, -100, 100}, {z, -30, 30}]
800000
The answer does not change when the upper limit of x changes.
Cheers,
Paul
--
Paul Abbott Phone: +61 8 9380 2734
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