Put to white the plot space outside a geometric shape

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Roderick
Roderick 2024-8-29
评论： DGM 2024-8-29
Dear all
I am using the attached colorbar to generate some plots, which looks like this:
As you can see, because the colorbar seems to not assign a plain white color to zeros, the background color outside the geometric shape has some residual color. How could I avoid this problem efficiently?

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Mathieu NOE
Mathieu NOE 2024-8-29
编辑：Mathieu NOE 2024-8-29
Ran in:
hello
have you checked that the colorbar is symetric around zero (to have white color correspind to zero exactly ? )
this requires to use caxis as in example below (the seond plot is "whiter" than the first one).
RdBu250cbrewer = readmatrix('RdBu_250_cbrewer2.txt');
Z = peaks(100) + 1 ;
% without caxis
figure(1),
imagesc(Z)
colormap(RdBu250cbrewer);
colorbar('vert')
% with caxis
figure(2),
zm = max(abs(Z),[],'all');
imagesc(Z)
colormap(RdBu250cbrewer);
caxis([-zm zm]) % force colors to be used symmetricaly so white correspond to zero
colorbar('vert')
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Mathieu NOE
Mathieu NOE 2024-8-29
there are lot's a colormap generators on Fex, for my fun I used this one :
Red White Blue Colormap - File Exchange - MATLAB Central (mathworks.com)
her's the result obtained (code below)
% with redwhiteblue
% (Fex : https://fr.mathworks.com/matlabcentral/fileexchange/86932-red-white-blue-colormap)
figure(3)
imagesc(Z)
zmin = min(Z,[],'all');
zmax = max(Z,[],'all');
colormap(redwhiteblue(zmin, zmax));
colorbar;
DGM
DGM 2024-8-29
I'll add that the RdBu map never reaches white in the center. It maxes out at [0.9686 0.9686 0.9686]. Since the given map is even length, it never actually includes this neutral color.

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