What is the Colormap for plotting weather radar velocity product with interval?

Question

Tunde Adubi 2022-6-5

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1734210-what-is-the-colormap-for-plotting-weather-radar-velocity-product-with-interval

编辑： Voss 2022-6-6

velocity plot.jpg

在 MATLAB Online 中打开

I need the velocity colormap that woud generate the python image attached.

This code does not work for matlab.

----------------------------------------------------------

figure('position',[50 100 1800 800])
pcolor(datenum(time),rng,zh)
datetick('x')
shading flat
set(gca,'color','w','LineWidth',1,'fontweight','bold','fontsize',15);
xlabel('\bf{Time (UTC)}','FontSize',12,'FontWeight','bold','color','k');
ylabel('\bf{Height (km)}','FontSize',12,'FontWeight','bold','color','k');
ylim([0.1 10])
caxis([-6 6])
title(['2021-12-24 ' ...
    'Velocity (m/s)']);
%mean_doppler_velocity
cb = colorbar;
cb.Label.String = 'Velocity (m/s)';
colormap vel

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Answer 1

Voss 2022-6-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1734210-what-is-the-colormap-for-plotting-weather-radar-velocity-product-with-interval#answer_979390

编辑：Voss 2022-6-5

在 MATLAB Online 中打开

velocity plot.jpg

You can take the colors directly from the colorbar in the image, and use them as your colormap:

data = imread('velocity plot.jpg');

cmap = permute(data(288:-1:27,903,:),[1 3 2]);

colormap(cmap)

colorbar();

Or maybe one of the colormaps here (or in another File Exchange submission) is similar enough:

https://www.mathworks.com/matlabcentral/fileexchange/68239-pycolormap4matlab

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Tunde Adubi 2022-6-6

在 MATLAB Online 中打开

Oh Thanks, but the exact colormap (name) is not in the list as seen in the link you shared. so, I used RdBu_r (a similar one) and didnt get the color. How do I used this (RdBu_r) in the script below.

%% data extraction from NetCDF file     
test_zh1 = ncread(fname,'mean_doppler_velocity');
zh = [zh,test_zh1];
%     off_set = double(ncreadatt(fname,'reflectivity','add_offset'));
%     scale_factor = double(ncreadatt(fname,'reflectivity','scale_factor'));
%     test_zh = (off_set) + scale_factor.*test_zh1;
%     zh = [zh,test_zh];
clear test_time test_zh1
end
figure('position',[50 100 1800 800])
pcolor(datenum(time),rng,zh)
datetick('x')
shading flat
set(gca,'color','w','LineWidth',1,'fontweight','normal','fontsize',10);
xlabel('\bf{Time (UTC)}','FontSize',10,'FontWeight','normal','color','k');
ylabel('\bf{Height (km)}','FontSize',10,'FontWeight','normal','Color','k');
ylim([0.1 10])
caxis([-20 50])
message = sprintf('2021-12-24\nEquivalent velocity Factor');
title(message, 'FontSize', 11,'FontWeight','bold','Color','k');
%mean_doppler_velocity
cb = colorbar;
cb.Label.String = 'Velocity (m/s)';
colormap RdBu_r

Walter Roberson 2022-6-6

I would suggest unique() by rows, as colorbar are guaranteed to have to have repeated rows if the number of entries in the map is fewer than the number of pixels used to plot the map.

Voss 2022-6-6

编辑：Voss 2022-6-6

在 MATLAB Online 中打开

velocity plot.jpg

@Tunde Adubi:

@Walter Roberson makes a good point. This will read the colormap colors from the colorbar portion of the image and remove any repeated colors:

% generating the colormap:

data = imread('velocity plot.jpg');

cmap = unique(permute(data(288:-1:27,903,:),[1 3 2]),'rows','stable');

% applying the colormap:

colormap(cmap)

colorbar();

In addition to that, I'll point out that you can save the colormap for your own use later (so you don't have to go through reading this .jpg each time you need this colormap) by storing it in a mat file:

save('blue_white_red.mat','cmap');

And load it later when you want to use it:

S = load('blue_white_red.mat')
S = struct with fields:
    cmap: [262×3 uint8]

and apply it at will:

figure();

pcolor(randn(50));

colormap(S.cmap);

colorbar();

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What is the Colormap for plotting weather radar velocity product with interval?

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