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

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!

[Ameer Hamza]

Can you give some example by attaching an image or some sample daatset?

[Ameer Hamza]

OP's comment moved here:

Hi Ameer!

Yes of course. This is the 2D matrix plotted with pcolor and a jet colormap.

And this is the 2D matrix, on the same region and dimensions: NaN where is white, buildings in blue, vegetation in green and some terrain in brown.

I need to assign the colors of the second matrix to the ame position in the first matrix. I know I can do that with "fill" but defining all the polygons would be too long.

Thanks for helping!

Simone

[Ameer Hamza]

First, I suggest you using the CLim property to make both images have the same color at the same values.

ax1 % this is the axis handle of the first axes
ax2 % this is the axis handle of the second axes
ax1.CLim = ax2.CLim;

[simone ferrari]

Thank you Ameer, done.

This is the new second image with the same axis values as the first one.

How should I continue?

[Ameer Hamza]

I appear that the values in the second image are not the same as in the first image. For example, the big green patch at the lower right of the second image is green (value around 10). Whereas, the same region is shown as dark blue in the first image (value around 1).

[simone ferrari]

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]

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

Answer 1

[Ameer Hamza]

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]');

[simone ferrari]

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

1. minor issue: the velocity values (field in the first image) are altered (but I can mix the images changing the colorbar);
2. 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

Answer 2

[simone ferrari]

Yes, sure!

In the .zip file you will find:

Example_Ameer.m (the main script)

loadmdm.m (a function to load matrices of matrices, as well as savemdm to save .mdm)

the .mdm files to generate the figures