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MathGroup Archive 2000

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Re: Weird Plot behavior...

  • To: mathgroup at smc.vnet.net
  • Subject: [mg22287] Re: Weird Plot behavior...
  • From: "Allan Hayes" <hay at haystack.demon.co.uk>
  • Date: Wed, 23 Feb 2000 01:01:20 -0500 (EST)
  • References: <88sn7o$ioh@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Doug,
You have some pretty steep peaks and valleys which it seem are not being
picked up.
Increasing PlotPoints helps:

Plot[{sf[sf[sf[sf[x]]]], x}, {x, 0, 1}]

Plot[{sf[sf[sf[sf[x]]]], x}, {x, 0, 1},
  PlotPoints -> 50]


Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565


<dougmckee at my-deja.com> wrote in message news:88sn7o$ioh at smc.vnet.net...
> I'm getting some strange, seemingly incorrect
> graphs from Mathematica 3:
>
> First I define a simple piecewise continuous
> function:
>
> sf[x_]:=If[x<(1/3),1-3 x,0.5 x - 1/6]
>
> Then I graph its 4th iterate on [0,1] (along with
> y=x):
>
> Plot[{sf[sf[sf[sf[x]]]],x},{x,0,1}]
>
> It's missing some information; in particular, the
> graph only shows 5 fixed points when I know there
> are 7.  And when I graph it on [0,2], I _do_ get
> all 7 fixed points, and, yes, they're all on
> [0,1]:
>
> Plot[{sf[sf[sf[sf[x]]]],x},{x,0,2}]
>
> What's going on?  Why is the first graph
> incorrect, and the second correct?
>
> Plot[{sf[sf[sf[sf[x]]]],x},{x,0,1},PlotDivision-
> >5]
>
> And here, even though I think I'm setting the
> PlotDivision _lower_ than the default (20), I get
> the right graph!
>
> Doug
>
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>



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