Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2004
*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 2004

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

Search the Archive

Re: Piecewise functions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg51561] Re: [mg51553] Piecewise functions
  • From: DrBob <drbob at bigfoot.com>
  • Date: Sat, 23 Oct 2004 00:21:41 -0400 (EDT)
  • References: <200410220222.WAA07319@smc.vnet.net>
  • Reply-to: drbob at bigfoot.com
  • Sender: owner-wri-mathgroup at wolfram.com

Clear@y
y[x_] /; x > 3 := x
y[x_] /; -1 < x < 3 := -x
y[_] := 1
Plot[y@x, {x, -2, 4}]

y/@{-1,3}

{1,1}

or

Clear@y
y[x_] := Which[x > 3, x,
     -1 < x < 3, -x,
     True, 1]
Plot[y@x, {x, -2, 4}]

y/@{-1,3}

{1,1}

or

Clear@y
y[x_] := 1 + (-1 - x) UnitStep[x + 1] + 2x UnitStep[x - 3]
Plot[y@x, {x, -2, 4}]

y/@{-1,3}

{1,3}

The last form has big advantages if you want to differentiate or integrate the function.

Bobby

On Thu, 21 Oct 2004 22:22:10 -0400 (EDT), Luca <luca at nospam.it> wrote:

> Hi all. I'm studying for the exam of signals and systems and I was
> trying to plot some kind of functions I transformed for exercise. So, I
> need to plot piecewise functions like:
>
> y(x) = x if x > 3
> y(x) = -x if -1 < x < 3
> y(x) = 1 else
>
> (should have been a system).
> I found out in the guide the chapter about this, and I learned that it
> is possible with the function UnitStep, which I know. Anyway, I found
> it difficult to determine the equation of the function using this
> method. Is it possible to do it simply writing everything like I did
> before, more or less? i.e. without having to determine the equation
> with the UnitStep function.
> Hope I've been clear enought. Many thanks.
>
> Luca
>
>
>
>



-- 
DrBob at bigfoot.com
www.eclecticdreams.net


  • Prev by Date: Re: Re: can't MATHEMATICA simplify simple expressions?
  • Next by Date: Re: [Help]How to reprensent the result in vector form?
  • Previous by thread: Re: Piecewise functions
  • Next by thread: Re: Piecewise functions