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Re: Defining function

• To: mathgroup at smc.vnet.net
• Subject: [mg44556] Re: Defining function
• From: "Curt Fischer" <crf3 at po.cwru.edu>
• Date: Fri, 14 Nov 2003 01:58:49 -0500 (EST)
• References: <bovtvd$nbc$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

"Ravinder Kumar B." <ravi at crest.ernet.in> wrote in message
news:bovtvd$nbc$1 at smc.vnet.net...
> Dear All,
> How to define a function over two different ranges in mathematica.
> For example
>
> f(t):= Exp[-i*t]  for t > 0   and
>      = 0          for t < 0
>
> Your response/clarification will be deeply appreciated.

One possibility is to use If[], but you will probably be better off if you
use UnitStep[]:

In[1]:=
f[t_] := UnitStep[t] Exp[-I t]
In[2]:=
Plot[Re[f[t]], {t, 0, 10}, PlotRange -> {{-2 Pi, 2 Pi}, {-1, 1}}]

Doing calculus with Integrate[] and the like works much, much better if you
use UnitStep.

-- 

Curt Fischer