Re: UnitStep in Mathematica 4.1
- To: mathgroup at smc.vnet.net
- Subject: [mg38204] Re: UnitStep in Mathematica 4.1
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Thu, 5 Dec 2002 03:30:23 -0500 (EST)
- Organization: Universitaet Leipzig
- References: <askg0q$l21$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
Unprotect[Integrate]
Integrate[UnitStep[-a_] UnitStep[a_], {a_, x1_?NumericQ, x2_?NumericQ}]
/;
Sign[x1*x2] < 0 := 0
Protect[Integrate]
Regards
Jens
Matt Pillsbury wrote:
>
> Hi,
>
> I have been relying on the UnitStep function in a project, and in
> general it seems to work pretty nicely. However, there is one simple
> problem that I'm having with it. Mathematica doesn't know that
>
> Integrate[UnitStep[-x] UnitStep[x], {x,-1,1}]
>
> should be zero. Is this because the integrand is 0 everywhere but at
> the origin, where it is 1, and Mathematica doesn't know what to do
> with the contribution from a set of measure zero? Or am I doing
> something else wrong?
>
> And is there a simple fix for my problem?
>
> Thanks,
> Matt Pillsbury