MathGroup Archive 2005

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

Search the Archive

a question about the UnitStep function


Dear Mathgroup, 
I want to let Mathematica compute the convolution of two sqare waves. I did as follows
 
f[x_]:=(UnitStep[x+1]-UnitStep[x-1])/2;
 
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. 
 


  • Prev by Date: Re: Weird behavior of SparseArray
  • Next by Date: Re: Periodic function Roots
  • Previous by thread: Re: Re: Re: Weird behavior of SparseArray
  • Next by thread: Re: a question about the UnitStep function