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Re: Defining function

• To: mathgroup at smc.vnet.net
• Subject: [mg44558] Re: Defining function
• From: Bill Rowe <readnewscix at mail.earthlink.net>
• Date: Fri, 14 Nov 2003 01:58:52 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

On 11/13/03 at 7:36 AM, ravi at crest.ernet.in (Ravinder Kumar B.) wrote:

> 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

There are several possible ways to do this. Any of the following will do:

f[x_]:=Exp[-I x]/;x>0
f[x_]:=0/;x<0

f[x_]:=If[x>0, Exp[-I x], 0]

f[x_]:= UnitStep[x] Exp[-I x]

Note, while each of these three methods will have the same plot they are not totally identical. The first leaves f[x] undefined at x = 0.
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