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RE: Questions on Plot

  • To: mathgroup at
  • Subject: [mg36759] RE: [mg36752] Questions on Plot
  • From: "DrBob" <drbob at>
  • Date: Mon, 23 Sep 2002 03:32:59 -0400 (EDT)
  • Reply-to: <drbob at>
  • Sender: owner-wri-mathgroup at

Try this:

<< Graphics`Colors`
n = 4096;
data = {w, x, y, z} = Array[Random[] &, {4, n, 2}];
g@{a_, b_} := ListPlot[a,
    PlotStyle -> {PointSize[0.005], b},
    DisplayFunction -> Identity,
    GridLines -> Automatic]
Show[g /@ Transpose[{data, {Red, Blue, Yellow, White}}],
    PlotRange -> {{0, 1}, {0, 1}},
    Axes -> Automatic,
    Frame -> True,
    DisplayFunction -> $DisplayFunction,
    Background -> GrayLevel[.026],
    ImageSize -> 500];

Bobby Treat

-----Original Message-----
From: Steve Gray [mailto:stevebg at] 
To: mathgroup at
Subject: [mg36759] [mg36752] Questions on Plot

I would appreciate help with these problems:

1. I'm plotting several thousand points, which I can do
either with something like this (this is a test):

w = Table[Point[{Random[], Random[]}], {i, 1, 4096}];
x = Table[Point[{Random[], Random[]}], {i, 1, 4096}];
y = Table[Point[{Random[], Random[]}], {i, 1, 4096}];
z = Table[Point[{Random[], Random[]}], {i, 1, 4096}];
dw = Graphics[{PointSize[0.01], RGBColor[ 1, 0, 0], w}];
dx = Graphics[{PointSize[0.01], RGBColor[.8, .8, .8], x}];
dy = Graphics[{PointSize[0.01], RGBColor[ 0, .5, .9], y}];
dz = Graphics[{PointSize[0.01], RGBColor[.8, .8, 0], z}];
Show[dw, dx, dy, dz, AspectRatio -> Automatic,
   PlotRange -> {{0, 1}, {0, 1}},
            Axes -> Automatic,
            Frame -> True,
   Background -> GrayLevel[.026],
   GridLines -> Automatic];

This gives me dots in 4 colors for distinguishing different
kinds of points in my real application. This works fine but
needs the Point structure. Or, I can do (this is for one
kind of point),

t = Table[{Random[], Random[]}, {i, 1, 1024}];
ListPlot[t, AspectRatio -> Automatic,
            Axes -> Automatic,
            Frame -> True,
   Background -> GrayLevel[.026]

which seems simpler and may fit into the rest of the program
more easily.

1. How do I get the RGBColor Rule or the equivalent into
the latter? The RGBColor[] call is not a rule.

2. In the latter case I also want to plot 4 types of points.
How do I get ListPlot to put down 4 plots superimposed?
Or can't I?

3. In either case, I need to make the whole plot area about
twice as big. That is, it now occupies about a 4" square. To
see details better in my real plot, and because with 16k points
the small plot just looks almost like a solid blur, I want to
make it more like 8" square, or as big as will fit the screen
(without changing the plot range or anything else). There
must be a scale factor somewhere.

Thank you for any information.

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