Nonlinear colormap for data that diverges

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Jared Erb 2024-2-10

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https://ww2.mathworks.cn/matlabcentral/answers/2080581-nonlinear-colormap-for-data-that-diverges

评论： Voss 2024-2-11

I have data that goes through divergences where the Z value goes from approximately -4000 to 4000 very rapidly in certain regions, but the vast majority of the data is near zero. In the picture below, to be able to see what is going on I had to scale most of the color values to near zero to properly see what is happening. But in doing so, most of the colors are in the tiny sliver near zero and the red and blue take up the rest. I would like to nonlinearly scale the colorbar to be able to see all of the colors being used and greatly shrink the red and blue color part of the bar, with leaving the raw data as is if possible. It would also be nice if the colorbar ticks would vary nonlinear as well, instead of being forced to have a set number between consecutive ticks.

%Simple Model of divergent data

X = linspace(-2,2,501) + 0.002;

Y = linspace(-2,2,501) + 0.002;

%Function with Positive and Negative Divergence, and most values near 0

Z = zeros(501,501);

for i=1:length(X)

for j=1:length(Y)

Z(i,j) = 1/((X(i) - 1)^2 + (Y(j) - 1)^2) - 1/((X(i) + 1)^2 + (Y(j) + 1)^2) + 5*(cos(X(i))+sin(Y(i)));

end

%Setting the colormap

factor = 0.3;

cmap = jet(1000);

map = 999*rescale(1000./(1+exp(-factor*([1:1000]-500))));

cmap2 = cmap(1+fix(map),:);

figure('Position',[200,100,1500,730]);

ax=axes;

[X,Y] = meshgrid(X,Y);

surf(X,Y,Z,'linestyle','none');

a = colorbar;

set(ax,'colormap',cmap2)

view([0,90])

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采纳的回答

Voss 2024-2-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2080581-nonlinear-colormap-for-data-that-diverges#answer_1406296

编辑：Voss 2024-2-11

在 MATLAB Online 中打开

How about something like this:

%Simple Model of divergent data

X = linspace(-2,2,801) + 0.002;

Y = linspace(-2,2,501) + 0.002;

%Function with Positive and Negative Divergence, and most values near 0

Z = 1./((X - 1).^2 + (Y.' - 1).^2) - 1./((X + 1).^2 + (Y.' + 1).^2) + 5*(cos(X)+sin(Y.'));

Z_scaled = sign(Z).*log10(1+abs(Z));

figure('Position',[200,100,1500,730]);

surf(X,Y,Z_scaled,'LineStyle','none')

view(2)

colormap(jet(1000))

cb = colorbar();

tl = [-10.^(5:-1:1) 0 10.^(1:5)];

cb.Ticks = sign(tl).*log10(1+abs(tl));

cb.TickLabels = tl;

Edited to use Z_scaled = sign(Z).*log10(1+abs(Z)); instead of Z_scaled = sign(Z).*log10(abs(Z));

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Jared Erb 2024-2-11

Yes, this is exactly what I wanted! Thank you so very much for all your help!

Voss 2024-2-11

You're welcome!

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更多回答（1 个）

Morgan 2024-2-10

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2080581-nonlinear-colormap-for-data-that-diverges#answer_1406281

在 MATLAB Online 中打开

Would something like this work for you?

% CALCULATE MESHGRID

xa = linspace(-2,2,501) + 0.002;

ya = linspace(-2,2,501) + 0.002;

[X,Y] = meshgrid(xa,ya);

% CALCULATE Z

Z = 1./((X - 1).^2 + (Y - 1).^2) - 1./((X + 1).^2 + (Y + 1).^2) + 5*(cos(X)+sin(Y));

% SCALE Z

ZS = sign(Z).*abs(log10(Z));

surf(X,Y,ZS)

axis equal tight

shading interp

colorbar;

view([ 0 90 ])

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Morgan 2024-2-10

Something like this, then?

Jared Erb 2024-2-10

Unforunately that doesn't work for negative values, but I would like to have a nonlinearity that isn't log based, as I couldn't get any log scaling to work correctly.

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