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Re: question (for Mathematica 6!)

  • To: mathgroup at
  • Subject: [mg75572] Re: [mg75519] question (for Mathematica 6!)
  • From: Murray Eisenberg <murray at>
  • Date: Sat, 5 May 2007 06:07:20 -0400 (EDT)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <>
  • Reply-to: murray at

One difference is that HeavisideTheta[0] is undefined, whereas 
UnitStep[0] is 1.  The docs say this: see the descriptions say this 
implicitly at the tops of the functions' "home pages"; the "Possible 
Issues" section on HeavisideTheta explicitly says "HeavisideTheta stays 
unevaluated for vanishing argument."

Another is that, as the docs say, Piecewise Expand does not operate upon 
HeavisideTheta because "it is a distribution and not a piecewise-defined 
function."  That is, PiecewiseExpand[HeavisideTheta[a]] just returns 
HeavisideTheta.  However, PiecewiseExpand[UnitStep[x]] returns, in 
InputForm, Piecewise[{{1,x>=0}},0].

dimitris wrote:
> I don't have a copy of Mathematica 6 but having spent much time
> reading the online documentation (not only because of curiosity!) I
> have one question...
> Can somebody explain me the introduction of the HeavisideTheta
> function
> in version 6?
> Note that the UnitStep function is still here
> Dimitris

Murray Eisenberg                     murray at
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305

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