Logarithmic Color Scale in a ListContourPlot

[raul...@gmail.com]

Dear All,

Is it possible to use a logarithmic scale in the colour legend of a ListContourPlot?

Thank you very much in advance for any help you can provide.

Best regards,
Raul

[Bob Hanlon]

data = Table[{
x = RandomReal[{-2, 2}],
y = RandomReal[{-2, 2}],
10^(x + 3 y/2)},
{1000}];

Module[{
min = Log[10, Min[data[[All, 3]]]],
max = Log[10, Max[data[[All, 3]]]]},
ListContourPlot[data,
PlotLegends -> Automatic,
Contours -> (Table[{2, 5, 10}*10^n,
{n, -1, 2}] // Flatten),
ColorFunction -> Function[{f},
ColorData["TemperatureMap"][(Log[10, f] - min)/(max - min)]],
ColorFunctionScaling -> False]]


Bob Hanlon

[djmpark]

It would help if you could post a specific case illustrating the problem,
perhaps in the context of a ContourPlot so responders would have an easy
starting point.

I'm guessing that your problem is that many contour levels come out having
the same color. If that is the case you could probably use the option
ColorFunctionScaling -> False, and then write a ColorFunction that mapped
the desired actual contour values to a range of 0 to 1 using a log function.

The Presentations Application has a ContourColors ColorFunction that assures
different colors for each contour region regardless of the spacings of the
contour values.

But you can probably tailor your own ColorFunction as indicated above.


David Park
djm...@comcast.net
http://home.comcast.net/~djmpark/index.html

[raul...@gmail.com]

Thanks Bob, it's a great solution! I also want to thank David for the help.

Best regards,
Raul