How to change the transparancy (FaceAlpha) of single bars in a bar plot

Hi,

I have a a code that plots data from a 14x4 array in a bar graph, I want to access entire groups of 4 bars (for example CDC19) so that I can change their transparancy.

b = bar(str2double(Out_Glycolysis_Fold(2:end,2:end)));
hold on
plot(xlim,[1 1], 'k')
hold off
xticklabels(Out_Glycolysis_Fold(2:end,1));
ylabel('Fold Change', 'FontSize', 13);
xlabel('Genes', 'FontSize', 13);
ax = gca;
ax.XTickLabelRotation = 45;
legend('Mid Exponential', 'Late Exponential', 'Early Diauxic', 'Mid Diauxic', 'Mid Stationary');
set(ax, 'FontSize', 15);
title(title_Glyc);
ylim([0.3 1.7])

ax = gca;
ob = ax.Children;
set(ob(2), 'FaceAlpha', 0.1

Only when I try to access for example the second group from the object it changes the transparancy of all the yellow bars, does anyone happen to know how to solve this?

Answer 1

[Ameer Hamza]

It seems from the documentation that changing individual bars like this isn't currently supported. The workaround is to create each bar as a separate object. For example, something like this

M = rand(3, 4);
alphas = [0.2 0.1 0.5 0.8;
          1 0.9 0.8 0.7;
          0.1 0.3 0.7 1]; % alpha value for all bars

f = figure();
ax = axes();
hold(ax);
for i = 1:size(M, 1)
    for j = 1:size(M, 2)
        bar(i + interp1([1 size(M, 2)], [-0.3 0.3], j), M(i, j), ...
            'BarWidth', 0.15, ...
            'FaceAlpha', alphas(i, j))
    end
end