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

MathGroup Archive 2008

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

Search the Archive

Re: How to plot discontinuous functions?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg90149] Re: How to plot discontinuous functions?
  • From: Szabolcs Horvát <szhorvat at gmail.com>
  • Date: Tue, 1 Jul 2008 06:56:22 -0400 (EDT)
  • References: <g4a6tv$8uh$1@smc.vnet.net>

Aaron Fude wrote:
> Hi,
> 
> If a function is defined via If, then when plotted it does not
> acknowledge the discontinuity. E.g.
> 
> f[x_] := If[x < 1, 1, 2];
> Plot[f[x], {x, 0, 2}, PlotRange -> {0, 3}]

Generally, it is not possible to detect discontinuities numerically. 
(Is the function 1/(1 + Exp[10000 x]) continuous at 0?)  Still, 
Mathematica does a pretty good job of finding them by analysing the 
expression the function is made of.  When it fails to detect a 
discontinuity, you can specify it manually:

Plot[f[x], {x, 0, 2}, PlotRange -> {0, 3}, Exclusions -> {1}]

(Look up Exclusions)


> 
> Defined via Piecewise, it does, but in my experience, not always:
> f[x_] := Piecewise[{{{1, 1}, x < 1}}, {2, 2}];
> Plot[f[x][[1]], {x, 0, 2}, PlotRange -> {0, 3}]
> 
> How do I make the Plot function try to acknowledge the discontuity by
> not connecting the left limit and the right limit?
> 
> Thanks,
> 
> Aaron
> 


  • Prev by Date: Re: How to plot discontinuous functions?
  • Next by Date: Draw two functions in a graph, one of them does also have a parameter.
  • Previous by thread: Re: How to plot discontinuous functions?
  • Next by thread: Re: How to plot discontinuous functions?