Put to white the plot space outside a geometric shape

Question

Richard Wood 2024-8-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2148639-put-to-white-the-plot-space-outside-a-geometric-shape

评论： DGM 2024-8-29

采纳的回答： Mathieu NOE

RdBu_250_cbrewer2.txt

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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Answer 1

Mathieu NOE 2024-8-29

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2148639-put-to-white-the-plot-space-outside-a-geometric-shape#answer_1507194

编辑：Mathieu NOE 2024-8-29

在 MATLAB Online 中打开

RdBu_250_cbrewer2.txt

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 2024-8-29

在 MATLAB Online 中打开

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 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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