How to determine the x-axis positions of the bars in a grouped bar chart

Suppose I make the following bar chart:

figure; bar([1 2],[3 4; 5 6])

How can I programatically find the x-axis locations of each of the bars? I don't want x = [1 2]. I want the actual locations of the blue and yellow bars.

Answer 1

[Allison]

the cyclist-

I ran into this same problem when switching from Matlab 2011b to 2015b, with the updated graphics engine. After fooling around for a bit, I found that the following code will work (adapted from your original post):

 %
mean_velocity = [5 6 7; 8 9 10]; % mean velocity
std_velocity = randn(2,3);  % standard deviation of velocity
figure
hold on
hb = bar(1:3,mean_velocity');
% For each set of bars, find the centers of the bars, and write error bars
pause(0.1); %pause allows the figure to be created
for ib = 1:numel(hb)
    %XData property is the tick labels/group centers; XOffset is the offset
    %of each distinct group
    xData = hb(ib).XData+hb(ib).XOffset;
    errorbar(xData,mean_velocity(ib,:),std_velocity(ib,:),'k.')
end

I'm not quite sure why the pause is required- it seems that the new graphics engine requires a little bit of time before it will recognize the figure handle properly. I've tried it in other scripts where there is more code in between the plotting and the additional math and it seems to work fine, as well as trying it just via command line, and found the same issue. This should work in any version r2014b+.

[David J. Mack]

The pause() enables the plot to be drawn. drawnow() would also work.

[Nga Dao Thi]

Thank you very much. It's useful for me!

[Tao Liu]

Thanks very much, useful for me

[Ajay Goyal]

What canbe done in case of MATLABR2013b

[Tasnuba Siddiqui]

Thank you very much. It's really useful and helped me a lot!

[Alex Wooten]

+1 for comment about pause. I had plotting code giving me different results when running line-by-line vs all at once, that explains it!

Answer 2

[Maxandre Jacqueline]

How to do this for a categorical x axis?

Answer 3

[Hossein]

Hi, Thank you for your answer, but unfortunately, there is no 'XOffset' property for the handle in Matlab 2017, does anyone have other ideas?

[the cyclist]

The code in Allison's answer works for me in version R2017b.

Are you sure you don't have some other problem?

[Hossein]

Mine was 2017a, now I tested on 2017b and it worked. :) Thank you for your reply.

Answer 4

[Shivkumar Vishnempet Shridhar]

There is a far simpler solution to this. Just split this into 2 bar plots. I've set the bar width as 0.2, so any x axis position you set, the bar should occupy x-width/2 to x+width/2

figure; bar([0.8 1.8],[3 4],0.2,'FaceColor',[0, 0.4470, 0.7410],'LineWidth',3)

hold on

bar([1.2 2.2],[5 6],0.2,'FaceColor',[0.9290, 0.6940, 0.1250],'LineWidth',3)

[Shivkumar Vishnempet Shridhar]

You can adjust you bar width or position as you please

[the cyclist]

This is the answer to a subtly different problem. This is the answer to "How do I place the bars at positions I choose?" I agree that it is easy to know the positions, if you have predefined them.

That is different from "How do I find the positions of the bars, after the MATLAB designers have placed them?"

They both have their uses.