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Re: a question about the UnitStep function

  • To: mathgroup at
  • Subject: [mg58438] Re: [mg58411] a question about the UnitStep function
  • From: Pratik Desai <pdesai1 at>
  • Date: Sat, 2 Jul 2005 04:06:57 -0400 (EDT)
  • References: <>
  • Sender: owner-wri-mathgroup at

Zhou Jiang wrote:

>Dear Mathgroup, 
>I want to let Mathematica compute the convolution of two sqare waves. I did as follows
>integrand=f[z] f[x-z];
>Assuming[Element[x, Reals], Integrate[integrand, {z, -Infinity, Infinity}]]
>Mathematica gave me the result as follows,
>((-1 + x) UnitStep[-1 + x] - x UnitStep[x] + (2 + x) UnitStep[2 + x])/4
>I plot the result to check 
>Plot[%,{x,-10,10}, PlotRange->All];
>It is clear wrong since the convolution of two square waves should be convergent. Can anyone give me some help with the subtlties about the UnitStep function? Any thoughts are appriciable. 
Try this,
integrand1=f[x] f[x-1]

Hope this is what your are looking for

Pratik Desai
Graduate Student
Department of Mechanical Engineering
Phone: 410 455 8134

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