How to make the color gradient gradual. In the plot
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How to make the colour gradient gradual. Note I want to use two colours -ve values in blue gradaul varies with values similarly for the +ve values with red .Data set is attached. I have tried it by grouping, it is working but not statisfied.
2 Comments
Sam Chak
on 16 Dec 2023
Is this red-to-blue color transition scheme good enough to represent contour levels in the Indian subcontinent?
Accepted Answer
DGM
on 16 Dec 2023
Edited: DGM
on 16 Dec 2023
I'm going to ignore the fact that using a smooth colorbar with discrete-valued data makes the plot unreadable. If you just want a colormap generator that sweeps between the four given colors, then here it is.
load India_data.mat
CT = bluered(10); % any even integer
scatter(lon,lat,20,rain,"filled");
xticks([66 74 82 90 98]);
xticklabels([66 74 82 90 98]);
ylim([6.5 39.5]);
yticks([8 14 20 26 32 38]);
colormap(CT); % C contains the 4 colors of choice
d = colorbar;
clim([-50 50])
%d.Ticks = linspace(1, 4, 9);
%d.TickLabels=["-40","","-20","","0","","20","","40"];
ylabel("Latitude","FontSize",16);
xlabel("Longitude","FontSize",16);
%ylabel(a,'RMSE','FontSize',16);
title('SSP126 2041-2070','FontSize',18);
The lack of contrast between the given colors isn't helping with readability, but that's what's given. You could use different colors.
CT = bluered_hicont(10); % any even integer
scatter(lon,lat,20,rain,"filled");
xticks([66 74 82 90 98]);
xticklabels([66 74 82 90 98]);
ylim([6.5 39.5]);
yticks([8 14 20 26 32 38]);
colormap(CT); % C contains the 4 colors of choice
d = colorbar;
clim([-50 50])
%d.Ticks = linspace(1, 4, 9);
%d.TickLabels=["-40","","-20","","0","","20","","40"];
ylabel("Latitude","FontSize",16);
xlabel("Longitude","FontSize",16);
%ylabel(a,'RMSE','FontSize',16);
title('SSP126 2041-2070','FontSize',18);
2 Comments
DGM
on 16 Dec 2023
You might also try looking on the File Exchange. There are many other similar diverging colormap generators.
More Answers (1)
Image Analyst
on 16 Dec 2023
The number of colors depends on the number of unique values in your data as well as the number of unique colors in your colormap.
Does this require the Mapping Toolbox? How did you plot this data?
It looks like your data has (perhaps) only 4 unique values. If so, you can get more by assigning the data to a digital image (matrix) and then use conv2 or imfilter to blur the image. Then create a colormap with more steps in it.
% Blur image
windowWidth = 5;
kernel = ones(windowWidth) / windowWidth^2;
blurredImage = conv2(yourImage, kernel, 'same');
% Create color map
numColors = 256;
redRamp = 1 : numColors;
blueRamp = numColors : -1 : 1;
greenRamp = zeros(numColors, 1);
cmap = [redRamp(:), greenRamp, blueRamp(:)];
% Display blurred image with colormap.
imshow(blurredImage, []);
colormap(cmap);
colorbar;
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