MATLAB: Coloring curves wrt to a third variable and creating legend for the same

colormaplegend

Hello, I need to plot 31 curves and their color needs to be according to a third variable that varies from 1 to 5. I tried writing the code as follows:
colorspec1 = colormap(jet(5));
for i = 1:31
    for j = 1:5
        if MA(i,2) == j
           semilogx(All_112(:,1), All_112(:,i+1),'-', 'Linewidth', 2, 'Color', colorspec1(j,:));
           hold all
        end
        legendInfo{j} = ['Wind Speed = ' num2str(j)];
     end
end
legend(legendInfo);
I am getting curves with varying colors, but something is wrong with the code as when I change the loop positions and define j before i, the color of some curves also changes, which should not happen. I am unable to fix this issue and would need your help. Another issue is that I need a legend with 5 different colored lines in the colormap to define the third variable, but unable to get that with this version of the code. Could you please give me some direction how to do that? Thanks.

Best Answer

There's no reason to loop over colors - you already have the index in MA(i,2). Assuming the second column of MA is restricted to 1:5, use this:
colorspec1 = colormap(jet(5));
hline = gobjects(31,1);
for ii = 1:31
  icolor = MA(ii,2);
  hline(ij) = semilogx(All_112(:,1),All_112(:,ii+1),'-', ...
    'Linewidth',2,'Color',colorspec1(icolor,:), ...
    'DisplayName',sprintf('Wind speed = %d',icolor));
  hold all
end
[~,inds] = unique(MA(:,2));
legend(hline(inds));
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