How to create a custom colormap in this case?

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BN
BN 2020년 5월 6일
댓글: BN 2020년 5월 6일
I want to know how I can change the color map and corresponding color bar to showing from light blue(#add8e6) to dark blue (#00008b).
S = shaperead ('country_Boundary.shp');
lon = S.X; % for example, I want to find all points in polygon number one
lat = S.Y;
plot(lon, lat, '-k')
hold on
axis equal
ax = gca;
xL = ax.XLim;
yL = ax.YLim;
rect_x = [-0.25 -0.25 0.25 0.25];
rect_y = [0.25 -0.25 -0.25 0.25];
x = points{:,1};
y = points{:,2};
z = points{:,3};
num_colors = 100;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
clrs = summer(num_colors); %<<<< here is the problem
zlim = [min(z) max(z)]+[-0.1 +0.1];
clr_val = @(z) clrs(ceil(interp1(zlim, [0 1], z)*num_colors), :);
for i=1:numel(x)
p(i) = patch(rect_x + x(i), rect_y + y(i), ...
clr_val(z(i)), ...
'EdgeColor', 'none');
end
ax.XLim = xL;
ax.YLim = yL;
colorbar
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
colormap(summer)
caxis([min(z) max(z)])
Thanks

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Sindar
Sindar 2020년 5월 6일
편집: Sindar 2020년 5월 6일
That is essentially the example here.
Using the hex -> rgb converter from this answer:
% test image
imagesc(rand(10,10))
colorbar
% define start and end colors
start_color = sscanf('add8e6','%2x%2x%2x',[1 3])/255;
end_color = sscanf('00008b','%2x%2x%2x',[1 3])/255;
N = 10;
% create a map linearly interpolating between them
% i.e. three columns interpolating from Red1 to Red2, etc.
map=[linspace(start_color(1),end_color(1),N)' linspace(start_color(2),end_color(2),N)' linspace(start_color(3),end_color(3),N)'];
colormap(map)
  댓글 수: 6
Sindar
Sindar 2020년 5월 6일
Note: from the error, it seems like you were trying to index the custom map directly:
clrs = map(num_colors);
The built-in colormaps (like summer) have a function that returns a colormap based on the number of colors you want. It is possible to replicate this behavior (by taking my code and putting it in a function of num_colors), but if you are directly building a map, it is an Nx3 matrix so you can't (and don't need to) tell it how many elements you want.
BN
BN 2020년 5월 6일
Thank you so much. I'll be grateful if you can look at another question of mine which is really similar. here is the link: https://www.mathworks.com/matlabcentral/answers/523398-is-it-possible-to-create-this-colormap-and-corresponding-colorbar-in-matlab
Thank you again

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