How to customize Colorbar on map?

8 views (last 30 days)
Shayma Al Ali on 13 Jan 2023
Edited: DGM on 13 Jan 2023
Hi everyone! I'm trying to recreate the Colorbar below. As you can see, the colorbar goes by increments of 0.01 until it gets to 0.1, then by 0.1 until it get to 1, and then values of 1 until it gets to 10, and so on. So a value around 2 would be colored as Orange on the plot.
I'm having trouble recreating this sort of colorbar.
My code:
figure(1)
worldmap([min(lat) max(lat)], [min(lon) max(lon)])
contourfm(lat,lon,chlor_a); hold on
geoshow(coastlat,coastlon,'Color','k','LineWidth',3)
%set colorbar to match NASA's
colormap(jet)
h=colorbar;
%colormap(jet)
h.Label.String='Chlor-a (mg m^-3)';
h.Label.FontSize=10;
clim([0.01 20]) %use NASA's color scale
title('Map of Chlorophyll-a Concentration off California Coast (07/12/2022 - 07/19/2022)')
How would I change the increments in the limits?

Sulaymon Eshkabilov on 13 Jan 2023
If you want to change a tickmarks only, then :
[X,Y] = meshgrid(-7:.25:7.5);
Z1 = X.^2 + Y.^2;
Z2 = Z1 + 10;
figure
surf(X,Y,Z1);
colorbar('Ticks', 0:20:100)
hold on

DGM on 13 Jan 2023
Edited: DGM on 13 Jan 2023
You should be able to set the axes colorscale to log.
% some fake data
x = linspace(0,1,100);
y = x.';
Z = 20*10.^(y-1) .* x;
% plot it somehow
pcolor(Z);
colormap(jet)
% set up a colorbar with log scale
cb = colorbar;
set(gca,'colorscale','log')
cb.Ticks = [0.01 0.02 0.05 0.1 0.2 0.5 1 2 5 10 20];
caxis([0.01 20])
If you additionally want to recreate the same colormap and don't know what it is, you can approximate it.
% read image and process it
rect = [92 79 991 33];
A = imcrop(A,rect);
CT0 = permute(mean(im2double(A),1),[2 3 1]);
CT0 = CT0([true; ~all(diff(CT0,1,1)==0,2)],:); % remove duplicate rows
% CT0 is now a fixed-length color table
% make it whatever length we want
N = 256; % specify the number of colors in table
na = size(CT0,1);
CT = interp1(linspace(0,1,na),CT0,linspace(0,1,N));
% then plot as before
figure
pcolor(Z);
colormap(CT)
% set up a colorbar with log scale
cb = colorbar;
set(gca,'colorscale','log')
cb.Ticks = [0.01 0.02 0.05 0.1 0.2 0.5 1 2 5 10 20];
caxis([0.01 20])
The difference is subtle, but I figured I'd add the option. Bottom is jet(256); top is the map taken from the image.

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