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MathGroup Archive 2004

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UnitStep Integration Rules

  • To: mathgroup at smc.vnet.net
  • Subject: [mg47668] UnitStep Integration Rules
  • From: "Reece, Daryl" <Daryl.Reece at goody.com>
  • Date: Tue, 20 Apr 2004 09:04:07 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Can someone help me understand what is happening here.  UnitStep causes
problems with Integrate, so I wanted to write my own replacement rule and
skip the problem.

Integrate[UnitStep[t/Month - 5],t]/. {Integrate[UnitStep[t/Month - 5],t] ->
(t - 5 Month) UnitStep[(t - 5 Month)/Month]}

yields:

(t - 5 Month) UnitStep[(t - 5 Month)/Month]

(....Great!!!!!!)

but

Integrate[UnitStep[t/Month - 5],t]/. {Integrate[UnitStep[t/Month - m_],t] ->
(t - m Month) UnitStep[(t - m Month)/Month]}

yields the unevaluated integral.  I've also tried m__ and m___ along with
various versions of the rule derived from the FullForm expression of the
above integral.  Why can't Mathematica make the substitution with the blank
expression in the rule?

Thanks,
Daryl


Daryl Reece
Goody

770.615.4807
810.885.0632


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