Adding error bars to a grouped bar plot

Hi! I’m trying to plot a grouped bar graph with standard errors, and have managed this so far, which almost works but the SE are for some reasons plotted next to the bars rather than on them (see attached)? Any idea how to fix it? Thanks!

err = [3, 3; 1, 3];
 
y=[69,123; 74, 62];
figure
bar(y)
set(gca, 'XTickLabel', {'Cats' 'Dogs'});
hold on
errorbar(y, err, '.')
ylabel('Mean Error');
ylim([20 140]);
legend('response to novel cats', 'response to novel dogs');
saveas(gcf,['bar_2', '.jpg'])

Answer 1

[Vishal Chaudhary]

The ability to specify that the "errorbar" function display the error bars inside the individual bars is not available in MATLAB. It displays errorbar at the center of each group.

To work around this issue, find the center of each bar and pass this data into "errorbar" with the respective error values.

ngroups = size(y, 1);
nbars = size(y, 2);
% Calculating the width for each bar group
groupwidth = min(0.8, nbars/(nbars + 1.5));
for i = 1:nbars
    x = (1:ngroups) - groupwidth/2 + (2*i-1) * groupwidth / (2*nbars);
    errorbar(x, y(:,i), err(:,i), '.');
end
hold off

[Shanaja]

Thank you so much, that worked perfectly!

[Sam Rabin]

A note: Using r2018b, I found that this answer does not work if the bar graph is constructed with a categorical X axis, like so:

bar(categorical({'Cats' 'Dogs'}),y)

The result is that the error bars are plotted at the group centers.

Instead, the bar graph should be constructed as in the original post:

bar(y)
set(gca, 'XTickLabel', {'Cats' 'Dogs'});

[David L]

This was super helpful. Thank you!!

[CR]

This is great! Would it be possible to decrease the spacing between the grouped bars? Thanks again!

Answer 2

[Steve Schaefer]

The code to create the below shown picture can be found in this MATLAB Answer:

https://www.mathworks.com/matlabcentral/answers/102220-how-do-i-place-errorbars-on-my-grouped-bar-graph-using-function-errorbar-in-matlab

[Jonathan Cottet]

@Steve Schaefer

The code for the graph is not really displayed in the link you posted (categorical graph in your picture). Could you please post it here ?

Thanks in advance !

[z8080]

@Steve Schaefer, I would second @Jonathan Cottet's request to please post that code, as it is in fact not to be found under the given link. Thanks!

Answer 3

[Star Strider]

An example using properties available in prior and recent MATLAB releases is provided in Putting error bars on bar plot?

One of these approaches should work for all releases (at least after R2014b when ‘Handle Graphics 2’ appeared, and perhaps for earlier releases as well). The same general approach will also work for putting numbers or other text objects above or within the bars.