How assign specific colours (different from the colourmap ones) to regions of a matrix

Question

simone ferrari 2020-4-5

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https://ww2.mathworks.cn/matlabcentral/answers/515573-how-assign-specific-colours-different-from-the-colourmap-ones-to-regions-of-a-matrix

评论： simone ferrari 2020-4-6

Hi!

After plotting a 2D matrix with pcolor and a jet colormap, I need to give some specific colours (e.g, black, green and brown)

to some specific regions of the figure (without using fill, too long to define every vertex). Thanks!

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simone ferrari 2020-4-5

Yes Ameer, that is my problem, how to put the green, brown and blue patches of figure 2 into figure 1 manteining the colours.

Ameer Hamza 2020-4-5

Can you attach you dataset as a mat file. It will make it easy for me to suggest a solution.

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Answer 1

Ameer Hamza 2020-4-6

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https://ww2.mathworks.cn/matlabcentral/answers/515573-how-assign-specific-colours-different-from-the-colourmap-ones-to-regions-of-a-matrix#answer_424236

在 MATLAB Online 中打开

Try this code.

xplot_ph0 = loadmdm('xplot_ph0');
yplot_ph0 = loadmdm('yplot_ph0');
WindSpeed_ph0 = loadmdm('WindSpeed_ph0');
U_ph0 = loadmdm('FlowuSpeed_ph0');
V_ph0 = loadmdm('FlowvSpeed_ph0');
Map_ed_veg = loadmdm('Edifici_vegetazione_ph0');
Map_ed_veg_NaN = Map_ed_veg;
Map_ed_veg_NaN(Map_ed_veg==0) = NaN;
passo=30;
fig=300;
fig = fig + 1;
figure (fig);
WindSpeed_ph0 = 4*WindSpeed_ph0; % 4 is selected by trial and error, tune it as required
WindSpeed_ph0(~isnan(Map_ed_veg_NaN)) = Map_ed_veg_NaN(~isnan(Map_ed_veg_NaN));
pcolor(xplot_ph0,yplot_ph0,WindSpeed_ph0);
shading flat; axis square; colormap jet; caxis([0 20]); colorbar;
xlabel('X [m]'); ylabel('Y [m]');
hold on
q=quiver(xplot_ph0(1:passo:end), yplot_ph0(1:passo:end), U_ph0(1:passo:end), V_ph0(1:passo:end), 2);
q.Color='black';
hold off
fig = fig + 1;
figure(fig);
pcolor(xplot_ph0,yplot_ph0,Map_ed_veg_NaN);
shading flat;axis square; colormap jet; caxis([0 20]); colorbar;
xlabel('X [m]'); ylabel('Y [m]');

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simone ferrari 2020-4-6

在 MATLAB Online 中打开

Thank you Ameer, but this does not completely solve my issue, as:

minor issue: the velocity values (field in the first image) are altered (but I can mix the images changing the colorbar);
major issue: this allows to set one colour each time, but not to use colour different from the ones of the colormap.

Anyway, following your idea I have created a new colormap reassigned values according to figure 2: results are better but not completely satisfying. This is the code:

close all;
clear all;
xplot_ph0 = loadmdm('xplot_ph0');
yplot_ph0 = loadmdm('yplot_ph0');
WindSpeed_ph0 = loadmdm('WindSpeed_ph0');
U_ph0 = loadmdm('FlowuSpeed_ph0');
V_ph0 = loadmdm('FlowvSpeed_ph0');
Map_ed_veg = loadmdm('Edifici_vegetazione_ph0');
Map_ed_veg_NaN = Map_ed_veg;
Map_ed_veg_NaN(Map_ed_veg==0) = NaN;
mycolormap1=jet;
mycolormap1(1,:)=[0 0 0];
mycolormap2=mycolormap1;
mycolormap2(256,:)=[1 1 1];
passo=30;
fig=0;
fig = fig + 1;
figure(fig);
pcolor(xplot_ph0,yplot_ph0,Map_ed_veg_NaN);
shading flat;axis square; colormap(mycolormap1); colorbar; caxis([1 20]); colorbar;
xlabel('X [m]'); ylabel('Y [m]');
WindSpeed_ph0_b =  WindSpeed_ph0;
WindSpeed_ph0_b(Map_ed_veg_NaN==1)=0;
WindSpeed_ph0_b(Map_ed_veg_NaN==11)=3;
WindSpeed_ph0_b(Map_ed_veg_NaN==15)=4.5;
fig = fig + 1;
figure (fig);
pcolor(xplot_ph0,yplot_ph0,WindSpeed_ph0_b);
shading flat; axis square; colormap(mycolormap1); colorbar;
xlabel('X [m]'); ylabel('Y [m]');
hold on
q=quiver(xplot_ph0(1:passo:end), yplot_ph0(1:passo:end), U_ph0(1:passo:end), V_ph0(1:passo:end), 2);
q.Color='k';
hold off
WindSpeed_ph0_b =  WindSpeed_ph0;
WindSpeed_ph0_b(Map_ed_veg_NaN==1)=0;
WindSpeed_ph0_b(Map_ed_veg_NaN==11)=max(WindSpeed_ph0(:))+0.01;
WindSpeed_ph0_b(Map_ed_veg_NaN==15)=max(WindSpeed_ph0(:))+0.01;
fig = fig + 1;
figure (fig);
pcolor(xplot_ph0,yplot_ph0,WindSpeed_ph0_b);
shading flat; axis square; colormap(mycolormap2); colorbar;
xlabel('X [m]'); ylabel('Y [m]');
hold on
q=quiver(xplot_ph0(1:passo:end), yplot_ph0(1:passo:end), U_ph0(1:passo:end), V_ph0(1:passo:end), 2);
q.Color='k';
hold off