Re: Curious problem with UnitStep
- To: mathgroup at smc.vnet.net
- Subject: [mg67891] Re: Curious problem with UnitStep
- From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
- Date: Wed, 12 Jul 2006 05:05:15 -0400 (EDT)
- Organization: Uni Leipzig
- References: <e8vtkn$sp0$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi, a serious reason to upgrade your Mathematica ... 5.2 work correct .. Regards Jens "hanspi" <hanspi at schmid-werren.ch> schrieb im Newsbeitrag news:e8vtkn$sp0$1 at smc.vnet.net... | Dear colleagues, | | I am trying to calculate the ACF of a combination of unit steps and its | fourier transform. There I see something very curious. | | I do: | | sw[t_, \[Tau]_] := UnitStep[\[Tau] - Abs[t]] | Plot[sw[t, 1.0], {t, -2, 2}] | | which looks OK. Then: | | akf[x_, \[Tau]_] := | Assuming[{t \[Epsilon] Reals, \[Tau] > 0}, | Integrate[ | sw[t, \[Tau]] sw[x - t, \[Tau]], {t, -\[Infinity], \[Infinity]}]] | Plot[akf[t, 1.0], {t, -2, 2}] | | Which also looks OK. | | But when I just type | | akf[t, 1.0] | | I get as an output | | 2. | | which is wrong, and also | | FourierTransform[akf[t, 1.0], t, \[Omega]] | | gives a wrong result. Why can I plot akf properly, but not evaluate | it? | | Hanspeter |