Changing transparency of individual bars in bar

I am trying to plot a 2D bar plot where I want to be able to control the transparency of individual bars. My code is as follows

bounds=categorical({'aa','bb','cc','dd','ee'});
bounds=reordercats(bounds,{'aa','bb','cc','dd','ee'});
%set(bounds,'Interpreter','latex');
legend('$\hat{\psi}$','Interpreter','latex')
vals=[1,2,3,4,5]
b=bar(bounds,vals);
b.FaceColor = 'flat';
b.CData(1,:) = [0 0 1];
b.CData(2,:) = [1 0 0];
b.CData(3,:) = [1 0 0];
b.CData(4,:) = [0 1 0];
b.CData(5,:) = [0 1 0];
b.AlphaData(1,:)=0.2
%b(1).FaceAlpha=0.2;
b.LineStyle=':';

I have tried two lines at the bottom using b.AlphaData and b(1).FaceAlpha, but these do not have the desired effect. The first gives an error and the code stops, whereas the second changes the transparency of all the bars simultaneously. Is there a way that I can for example set the 2nd and 4th plots to be transparent (e.g. 0.3) and have dotted outlines, while not changing bars 1, 3 and 5?

Answer 1

[Adam Danz]

You can plot the bars one at a time or in groups that all have the same FaceAlpha level.

That way the bars with differen alpha levels are independent and have their own properties.

Demo:

bounds=categorical({'aa','bb','cc','dd','ee'});
bounds=reordercats(bounds,{'aa','bb','cc','dd','ee'});
%set(bounds,'Interpreter','latex');
% legend('$\hat{\psi}$','Interpreter','latex')
vals=[1,2,3,4,5];

colors = [0 0 1; 
    1 0 0; 
    1 0 0; 
    0 1 0; 
    0 1 0];

alphas = linspace(.08,.9, numel(bounds)); 

b = gobjects(size(bounds)); 
cla()
hold on
for i =1:numel(bounds)
    b(i)=bar(bounds(i),vals(i));
    set(b(i),'FaceColor',colors(i,:),'FaceAlpha',alphas(i)); 
end
grid on

[Lorcan Conlon]

Thank you. Is there also a simple way to overlap bars bb and cc? So they have the same x coordinate but there will be two different heights, which I am distinguishing between by using a dashed linestyle for bb and a solid linestyle for cc.

Thanks!

[Adam Danz]

You'll need to temporarily assign them then same category if you want them to share the same x-coordinate.

Then you can change the xticklabel.

bounds=categorical({'aa','bb','bb','dd','ee'}); % skip the reordercats line
%                         ↑↑   ↑↑

ax = gca(); 
b(2).LineStyle = '--';
ax.XTickLabel{2} = sprintf('bb\\newlinecc');

[Lorcan Conlon]

Thanks again. One more question.. If I want to arrange my plot so that dd comes second and then the bb/cc bar, do you know how I can do this? Matlab seems to force them into alphabetical order once I remove the reordercats line.

Thanks!

[Adam Danz]

You'll need to put the reordercats line back in. I removed it just for my demo.

However, do not override the categorical name until after reordering.

[Lorcan Conlon]

reordercats doesn't appear to work with duplicated values however. Is there a way around this?

[Adam Danz]

You shouldn't duplicate anything in the 'neworder' vector. My last comment says "do not override the categorical name until after reordering".

So,

1. Define the categorical values: bounds=categorical({'aa','bb','cc','dd','ee'});
2. Do the reordering: bounds=reordercats(bounds,{'aa','bb','cc','dd','ee'});
3. Now switch the cc to bb

There are lots of ways to do that. The method in my answer is just to demonstrate the main idea so you can take it from there. For example, you could do,

bounds(3) = categorical({'bb'}); 

but now an empty space will appear in the bar plot where cc should go.

Another method is,

1. Define the categorical values: bounds=categorical({'aa','bb','cc','dd','ee'});
2. Switch cc to bb before reordering
3. Do the reordering but don't include cc: bounds=reordercats(bounds,{'aa','bb','dd','ee'});

Now there won't be any empty spaces in the bar plot for cc.