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Topic: ListPlot - assigning a list of colors to a set of
Replies: 6   Last Post: Nov 6, 2013 12:29 AM

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Gordon Robertson

Posts: 18
Registered: 11/15/07
Re: ListPlot - assigning a list of colors to a set of
Posted: Nov 6, 2013 12:23 AM
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Thanks Bob,

Your solutions are compact. The code below extends your first example to use a long list of XY coordinates and colours in ListPlot.

nbr = 1000
xy = Transpose[{RandomReal[{0, 1}, nbr], RandomReal[{0, 1}, nbr]}]; (* xy data to plot *)
cols = Table[RandomChoice[{Red, Green, Blue}], {i, nbr}]; (* list of colors *)

ListPlot[List /@ xy, PlotStyle -> (Directive[PointSize[0.02], Opacity[0.6], #] & /@ cols)]


On 2013-11-05, at 8:34 AM, Bob Hanlon wrote:

Make each point a separate data list and repeat the PointSize:

ListPlot[List /@ {{1, 1}, {2, 2}, {3, 3}},
PlotStyle -> (Directive[PointSize[0.02], #] & /@
{Red, Green, Blue})]

Although you can use a List instead of Directive:

ListPlot[List /@ {{1, 1}, {2, 2}, {3, 3}},
PlotStyle -> ({PointSize[0.02], #} & /@
{Red, Green, Blue})]


ListPlot[List /@ {{1, 1}, {2, 2}, {3, 3}},
PlotStyle -> {Red, Green, Blue},
PlotMarkers -> {Automatic, Medium}]

Bob Hanlon

On Mon, Nov 4, 2013 at 11:16 PM, Gordon Robertson <grobertson@bcgsc.ca<mailto:grobertson@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.

Thanks very much for your help.

Gordon Robertson
Michael Smith Genome Sciences Centre
BC Cancer Agency
Vancouver BC Canada

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