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Re: newby plotting question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg22756] Re: [mg22711] newby plotting question
  • From: "Tomas Garza" <tgarza at mail.internet.com.mx>
  • Date: Fri, 24 Mar 2000 03:28:00 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

F. Schwieterman wrote:

> I have three lists I want to plot on the same graph, in different colors.
> My code went as follows:
> (mean and var are lists of numbers, of the same length)
>
> p1 = ListPlot[ mean, PlotRange->All];
> p2 = ListPlot[ mean + Sqrt[var],
>             DefaultColor -> RGBColor[0,1,0], PlotRange->All];
> p3 = ListPlot[ mean - Sqrt[var],
>             DefaultColor -> RGBColor[1,0,0], PlotRange->All]];
> Show[p1,p2,p3];
>
>
> But this unfortunately draws p1, p2, and p3 on separate plots
> before drawing
> all three on a single plot, and they were all black on the last
> plot anyhow.
>
> So I was clever, and came up with the following:
>
> Show[
>           ListPlot[ mean, PlotRange->All],
>           ListPlot[ mean + Sqrt[var],
>             DefaultColor -> RGBColor[0,1,0], PlotRange->All],
>           ListPlot[ mean - Sqrt[var],
>             DefaultColor -> RGBColor[1,0,0], PlotRange->All]]
>
> Which produces the same result.  ugh.  Any advice?

Cf. the Help Browser under Show:"When plots are combined, their lists of
non-default options are concatenated." You are combining plots p1, p2, p3
and hence the non-default options are concatenated. This means that you are
in effect concatenating  DefaultColor -> RGBColor[0,1,0] and DefaultColor ->
RGBColor[1,0,0]. Hence you have a conflict, and Show reconciles this problem
by using the options of the first object (see Wickham-Jones book on
Mathematica Graphics, p.232), in your example p1. Try Show[p2,p1,p3] and
you'll see a different color for the combined graph. But I guess you only
want to apply colors to the points, not to the axes and the rest of the
plot. Then I suggest you use PlotStyle instead of DefaultColor. This will do
the trick. BTW, if you only want to display the combined graph, use the
option DisplayFunction->Identity in each of p1, p2 and p3, and then
DisplayFunction->$DisplayFunction in Show. This saves a lot of space in your
notebook.

Tomas Garza
Mexico City



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