How to make the contour labels (numbers) use the same color as the contour lines?

Dear MATLAB users,

I want to know if it is possible to make clabel follow the color of the contours? Meaning that the numbers have the same color as the contour curves.

Here is an example which could be produced using MATLAB, and I am trying to reproduce it.

[This figure is taken from: Phase coherence in graphene by Mark Brian Lundeberg]

This is my MATLAB codes.

% Phase coherence in graphene 石墨烯中的相位相干.pdf, Page 9

clearvars; clc; close all; fclose all; format short; format compact;

a = 1;

t = 1;

kx = linspace(-4*pi/(sqrt(3)*a), 4*pi/(sqrt(3)*a), 101);

[KX, KY] = meshgrid(kx, kx);

energy = t * sqrt(3 + 2*cos(KY*a) + 4 * cos((sqrt(3)/2)*KX*a) .* cos((1/2)*KY*a));

fig = figure('Unit', 'Centimeter', 'Position', [1, 1, 12, 12]);

% ax = axes(fig, 'Unit', 'Centimeter', 'Position', [2, 2, 8, 8]);

ax = axes(fig);

hold on;

[C, h] = contour(ax, KX, KY, energy, 'LineWidth', 0.5);

% https://ww2.mathworks.cn/matlabcentral/answers/83483-labels-on-the-contour-have-too-many-digits

h.LevelList = round(h.LevelList, 3);

clabel(C, h, 'FontSize', 8, 'FontName', 'Arial');

h.LevelList = 0.30:0.20:3.00;

colormap(jet)

% Draw a regular hexagon (e.g., Brillouin zone)

theta = (30:60:360)*pi/180;

vert = (4*pi/(3*a)) * [cos(theta); sin(theta)]; % vertices of hexagon

pgon = polyshape(vert');

plot(pgon);

axis equal;

% saveas(fig, 'TBA_bands_hexagonal_contour', 'pdf');

This is the result.

Best regards,

Qilin.

[Adam Danz]

Those clabels are following the contour.

[Voss]

I think OP wants the color of each text label to match the color of its associated contour line.

[Adam Danz]

Oh, I see that now. Sorry @qilin guo and thanks @_.

[DGM]

This should be possible if using clabel() in 'manual' mode. In that case, the labels are text objects. You could find them, find their corresponding levels and set their color according to the colormap. It might end up being somewhat similar to this task:

https://www.mathworks.com/matlabcentral/answers/1646510-clabel-line-break-for-label

That said, you're not using manual mode, and manual mode would be a pain to use here anyway. In that case, the labels aren't text objects. You can set all the labels to a common color via the clabel() call, but you can't specify a colormap. I don't even know how you'd access them, though I suspect that there are undocumented ways.

[qilin guo]

@Adam DanzDon't worry.

[qilin guo]

@DGMThank you!

Answer 1

[Adam Danz]

Generate contour with level labels

Adapted from OP's code:

a = 1;
t = 1;
kx = linspace(-4*pi/(sqrt(3)*a), 4*pi/(sqrt(3)*a), 101);
[KX, KY] = meshgrid(kx, kx);
energy = t * sqrt(3 + 2*cos(KY*a) + 4 * cos((sqrt(3)/2)*KX*a) .* cos((1/2)*KY*a));
fig = figure();
ax = axes(fig); 
hold on;
[C, h] = contour(ax, KX, KY, energy, 'LineWidth', 0.5);
h.LevelList = 0.30:0.20:3.00;
clabel(C, h, 'FontSize', 8, 'FontName', 'Arial');
colormap(jet)

Set contour label colors to contour colors

• h is the contour handle from [~,h]=contour(__)
• ax is the axes handle

drawnow() % required
ax.CLim = [min(h.LevelList), max(h.LevelList)];
clabelVals = str2double(get(h.TextPrims, 'string')); 
levelNorm = (clabelVals-ax.CLim(1))./(ax.CLim(2)-ax.CLim(1));
colorIdx = round(levelNorm * (size(ax.Colormap,1) - 1))+1;
clabelRGB = uint8([ax.Colormap(colorIdx,:) * 255, zeros(numel(colorIdx),1)])';
set(h.TextPrims, {'ColorData'}, mat2cell(clabelRGB,4,ones(1,size(clabelRGB,2)))');

Answer 2

[Alexandre]

As of MATLAB R2023b we have introduced a new Property Input for LabelColor on Contour called 'flat', which will map each Contour Label's Color to the colormap. This color mapping will be equivalent to the Line color mapping, as such, each Contour Label Color will match its associated Contour Line Color.

Please look at our updated documentation for more information:

Contour Properties | Label Color

Updated OP Code:

a = 1;
t = 1;
kx = linspace(-4*pi/(sqrt(3)*a), 4*pi/(sqrt(3)*a), 101);
[KX, KY] = meshgrid(kx, kx);
energy = t * sqrt(3 + 2*cos(KY*a) + 4 * cos((sqrt(3)/2)*KX*a) .* cos((1/2)*KY*a));
fig = figure();
ax = axes(fig);

[C, h] = contour(ax, KX, KY, energy, 'LabelColor', 'flat', 'LineWidth', 0.5);
h.LevelList = 0.30:0.20:3.00;
clabel(C, h, 'FontSize', 8, 'FontName', 'Arial');
colormap jet

Simple Example:

contour(peaks, 'LabelColor', 'flat')

Please look at Adam Danz's answer for how to workaround this limitation in previous releases.