Plot a 2-dimensional matrix with 2 different colormaps for negative and positive values

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THONTI BEERAIAH 2023-8-25

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https://ww2.mathworks.cn/matlabcentral/answers/2012682-plot-a-2-dimensional-matrix-with-2-different-colormaps-for-negative-and-positive-values

评论： Dyuman Joshi 2023-8-28

I have a big matrix consisting of values ranging from negative to positive. When I plot that by just imagesc and apply colorbar it is shpwoing gradiant over all. My requirement is to apply one colormap for negative values (probably cool) and the other colormap for positive values (probabliy hot) in a same plot as attached ( so there will be clear difference between negative and positive values).

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Answer 1

Dyuman Joshi 2023-8-25

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https://ww2.mathworks.cn/matlabcentral/answers/2012682-plot-a-2-dimensional-matrix-with-2-different-colormaps-for-negative-and-positive-values#answer_1294032

编辑：Dyuman Joshi 2023-8-25

在 MATLAB Online 中打开

%Random data for example

y = (-7:5)+(-7:5)';

%Get the maximum and minimum values of the array

p = max(y,[],'all');

n = min(y,[],'all');

%Display via imagesc

imagesc(y)

%Two colormaps

col = [cool(abs(n));hot(p)];

%Multiply the input with the same number to get more divisions on colors

%col = [cool(3*abs(n));hot(3*p)];

cb = colorbar('Ticks',n:p);

colormap(col)

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THONTI BEERAIAH 2023-8-28

ap_avg.txt

Thank you, however you solution worked nice for matrix with integers. I have a matrix which has noninteger values where the method is not working. I am uploading one matrix (as text file) so could you please do the same for the uploaded data?

Dyuman Joshi 2023-8-28

在 MATLAB Online 中打开

For non-integer values, round the values away from zero -

%Random data for example

vec = (-7.5:0.5:5);

y = vec+vec';

%Get the maximum and minimum values of the array

p = max(y,[],'all');

n = min(y,[],'all');

%As the input to colormaps must be positive (because it's an index)

%to round away from zero, we take ceil() of the absolute value

f = @(x) ceil(abs(x));

%Display via imagesc

imagesc(y)

%Two colormaps

col = [cool(f(n));hot(f(p))];

cb = colorbar('Ticks',n:p);

colormap(col)

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Plot a 2-dimensional matrix with 2 different colormaps for negative and positive values

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