Color map from green to red

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Idan Hamawi
Idan Hamawi 2020-10-17
编辑： DGM 2022-4-19
Hi all,
I have a map with values and i would like to display the values with colors - from green to red.
The value closest to 0 will be green and the farthest will be red.
Example:
1, 5, 11, 33, 56, 100
1 - Green.
100 - Red.
Can be also:
-5, -23, -43, -55, -80.
-5 - Green.
-80 - Red.
The rest values will be in the order and color bar.

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采纳的回答

Akira Agata
Akira Agata 2020-10-17
You can create your original colormap (green to red) and apply to the data.
The following is an example:
% Create green-to-red colormap
cMap = interp1([0;1],[0 1 0; 1 0 0],linspace(0,1,256));
% Apply to the plot
surf(peaks)
colormap(cMap)
colorbar
  4 个评论
显示 2更早的评论
Harpreet Singh
Harpreet Singh 2022-4-19
But that is a one way gradient. Didn't Akira want a two way gradient? with gren being in the middle and red going outwards?
DGM
DGM 2022-4-19
编辑：DGM 2022-4-19
Ran in:
I don't really think OP was after an RGB sweep, but more of an HSV hue sweep. Still, if Akira's solution was enough, then it could be made symmetric.
% Create red-green-red colormap
cMap = interp1(0:2,[1 0 0; 0 1 0; 1 0 0],linspace(0,2,256));
% Apply to the plot
surf(peaks)
colormap(cMap)
colorbar
FWIW, for simple RGB primary/secondary sweeps like this, you can improve the linearity to get rid of the dark bands:
% Create red-green-red colormap
cMap = interp1(0:1,[0 1 0; 1 0 0],linspace(0,1,256));
cMap = cMap.^(1/2.4); % linearize
% Apply to the plot
surf(peaks)
colormap(cMap)
colorbar
This gamma adjustment of colormaps can also be done using the misleadingly-named brighten() function, though the parameter behavior is (in my opinion) confusing in the degree to which it obfuscates the otherwise extremely simple math.
Gimme a minute and I'll whip up a colormap that replicates the exact map that OP posted.

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更多回答（1 个）

DGM
DGM 2022-4-19
编辑：DGM 2022-4-19
Ran in:
This is how one might go about getting the exact colormap shown in the image and make a symmetric version of it.
A = imread('gyrcb.png');
imshow(A)
% get base color table from image
basect = im2double(permute(A(40,24:517,:),[2 3 1]));
N = 256;
nb = size(basect,1);
% interpolate to get a specified-length version
CT1 = interp1(1:nb,basect,linspace(1,nb,N));
% also make a symmetric version of the same length
CT2 = interp1(1:2*nb,[flipud(basect); basect],linspace(1,2*nb,N));
% Apply the new CT
surf(peaks)
colormap(CT1)
colorbar
% Apply the symmetric CT
figure
surf(peaks)
colormap(CT2)
colorbar
Similar questions:
colorbar extraction (a discrete colormap)
https://www.mathworks.com/matlabcentral/answers/1591314-how-to-make-colormaps-like-the-attached-colorbar
colorbar extraction (includes notes about dealing with compression artifacts)
https://www.mathworks.com/matlabcentral/answers/1622300-how-to-create-rainbow-colormap-with-violet

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