Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2003
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2003

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: piecewise definition of a function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg43890] Re: [mg43870] piecewise definition of a function
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Fri, 10 Oct 2003 03:06:00 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

On Thursday, October 9, 2003, at 02:55 PM, Nathan Moore wrote:

> I'd like to define a function in a piecewise manner.  As of yet I've
> been unsuccessful with even the simplest example.  Consider the
> following:
>
> first define a 1-d bump,
>
> f[x_] = If[x < 0, 0,If[x > 1, 0, 1]]
>   Mathematica doesn't seem to mind this, as f[0.1] evaluates 1 and
> f[-23] evaluates 0.
> The problem comes when I try to integrate the function.  The
> following command which should evaluate to 1 doesn't work AT ALL!
>
> Integrate[f[x], {x, -50, 50}]
>
> What is the proper technique here?
>
> Nathan Moore
> University of Minnesota Physics
>
>
>
The correct way to approach to do this in connection with integration 
is by using the UnitStep function:

f[x_] := UnitStep[x]UnitStep[1 - x]

In[11]:=
Integrate[f[x],{x,-50,50}]

Out[11]=
1




Andrzej Kozlowski
Yokohama, Japan
http://www.mimuw.edu.pl/~akoz/
http://platon.c.u-tokyo.ac.jp/andrzej/


  • Prev by Date: Re: piecewise definition of a function
  • Next by Date: Re: piecewise definition of a function
  • Previous by thread: Re: piecewise definition of a function
  • Next by thread: RE: piecewise definition of a function