How do I bind a specific value to a color using colormap?

Question

Denis Perotto 2019-1-15

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https://ww2.mathworks.cn/matlabcentral/answers/439856-how-do-i-bind-a-specific-value-to-a-color-using-colormap

回答： Walter Roberson 2019-1-16

I'm plotting a 2D contour plot using contourf(X, Y, Z). How can I create a custom colormap, where certain color would be bound to a curtain value? For example:

100 - [1 0 0]

200 - [1 0.5 0]

1000 - [1 1 0]

It would be also nice to make all values below 100, for example, [0.5 0 0] and all values above 1000 - [1 1 0.5].

Please, do not suggest colormap editor. If this task is impossible for colormap, suggest me another function for 2D plots (maybe, plot it dot by dot)

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Walter Roberson 2019-1-16

To confirm: if the input value were 100*(1+eps) then the output should be transparent because the value would not be any of the ones you listed?

Denis Perotto 2019-1-16

I meant non-even intervals:

-inf ... 100 - [0.5 0 0]

100-200 - [1 0 0]

200-1000 - [1 0.5 0]

1000 ... inf - [1 1 0]

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Answer 1

Walter Roberson 2019-1-16

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https://ww2.mathworks.cn/matlabcentral/answers/439856-how-do-i-bind-a-specific-value-to-a-color-using-colormap#answer_356598

See https://www.mathworks.com/matlabcentral/answers/377542-how-can-i-change-number-on-colorbar-caxis#answer_300478

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Answer 2

KSSV 2019-1-15

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https://ww2.mathworks.cn/matlabcentral/answers/439856-how-do-i-bind-a-specific-value-to-a-color-using-colormap#answer_356479

Refer this link for the same:

https://in.mathworks.com/matlabcentral/answers/375166-how-to-customize-a-colorbar-of-contourf-plot-such-that-different-colors-are-for-values-in-different

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Denis Perotto 2019-1-16

编辑：Denis Perotto 2019-1-16

在 MATLAB Online 中打开

Tricky, but not acceptable for me.

First, there is a need to see real, not modified, data at any point on a contour, when I move my mouse on that point.

Second, I anyway get an even distribution of colors, which I cannot control. I created a custom colormap of 8 colors and set up 8 intervals. But the cycle, which modifies data, sets all the values to the maximum, and I miss 1 color anyway. I tried to program it like this:

crange = [0 TS-(TL-TS) TS-0.5*(TL-TS) TS TS+0.25*(TL-TS) TS+0.5*(TL-TS) ...
    TS+0.75*(TL-TS) TL max(max(Z))+0.01]';
crange(1:size(crange, 1)-1, 2) = crange(2:size(crange, 1), 1);
crange = crange(1:size(crange, 1)-1,:);
cmap = [0 0 1;
        0 0.5 1;
        0 1 1;
        1 0 0;
        1 0.4 0;
        1 0.6 0;
        1 0.8 0;
        1 1 0];
colors = zeros(size(Z));
for c = 1:size(crange, 1)
    for i = 1:size(Z, 1)
        for j = 1:size(Z, 2)
            if Z(i, j) >= crange(c, 1) && Z(i, j) < crange(c, 2)
                colors(i, j) = crange(c, 2);
            end
        end
    end
end
contourf(X, Y, colors);
colormap(cmap);
colorbar