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Re: ListPlot - assigning a list of colors to a set of points

  • To: mathgroup at smc.vnet.net
  • Subject: [mg131960] Re: ListPlot - assigning a list of colors to a set of points
  • From: Joe Gwinn <joegwinn at comcast.net>
  • Date: Wed, 6 Nov 2013 00:37:04 -0500 (EST)
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  • References: <l59r3a$rcm$1@smc.vnet.net>

In article <l59r3a$rcm$1 at smc.vnet.net>, Gordon Robertson
<grobertson at bcgsc.ca> wrote:

> I'm using Mathematica v9.x on a Mac, with OS X 10.7.5.
> 
> Could I ask about something that likely has a very simple solution? I have a
> list of XY coordinates for say 500 points that will become a scatterplot via
> ListPlot. I need to assign a colour to each point, using a list of labels
> (histology, risk, =85).
> 
> I've generated ArrayPlot graphics for cases like this for some time. For
> example, given some labels in column 4 of a 'hist' table:
> colours = Table[{
>     Switch[name = hist[[i, 4]],
>      "Classical", Green, "Tall cell", Red, "Other", Blue]
>     }, {i, Length[hist]}];
>  ArrayPlot[{colours}, AspectRatio -> 0.1, Frame -> False]
> 
> For a ListPlot, I'd have thought that something as simple as dropping a list
> of colours into a PlotStyle Directive would do the job. But the following
> line plots three blue points, rather than a Red, Green and Blue point.
> ListPlot[{{1, 1}, {2, 2}, {3, 3}},
>  PlotStyle -> Directive[PointSize[0.02], {Red, Green, Blue}]]
> 
> Is there a simple way to declare a list of colours in ListPlot? I've looked
> through the PlotStyle documentation, and apologize if I've missed seeing how
> to do this.

I never did figure out how to do that with ListPlot, and Tech Support
didn't know of a way either, so I built the plot-list directly, as a
Graphics[] object, and then used Show[] to display it, and to overlay
the colored dots on various function lines from ListPlot.

Joe Gwinn



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