Grouped error bars change position after saving figure

I have a grouped bar graph with error bars (3 groups, 5 bars each, 15 bars and error bars total). When the figure is first created, the plot looks fine, but when I save (using file>saveas in the figure window) and repoen the figure, the error bars move from being centered on their respective bars (correct) to being centered on each group (incorrect). I've scowered the figure and errorbar property lists for a setting that might prevent this with no luck and there doesn't seem to be any other posts here that address this issue either.

Code

barHeights = [0.954, 0.666, 0.604, 0.842, 0.662;...
              0.021, 0.280, 0.259, 0.145, 0.212;...
              0.027, 0.075, 0.100, 0.022, 0.084];
barErrors = [0.023, 0.057, 0.091, 0.056, 0.081;...
             0.007, 0.046, 0.080, 0.053, 0.091;...
             0.018, 0.029, 0.029, 0.016, 0.034];
[nGroups,nBars] = size(barHeights);
groupNames = categorical("Group" + string(1:nGroups));
barNames = "Bar" + string(1:nBars);
figure;
hold on
b = bar(groupNames,barHeights,'FaceColor','flat');
title("Title");
xlabel("xlabel");
ylabel("ylabel");
grid on;
x = reshape([b.XEndPoints],[nGroups,nBars]);
errorbar(x,barHeights,barErrors,'k','linestyle','none');
legend(barNames);
hold off

Figure: Before Saving (CORRECT)

Figure: After Saving and Reopening (INCORRECT)

[Andrew Soltisz]

I notice that when I set the error bar 'XDataMode' of the correct/original figure from 'manual' to 'auto', the error bars move from their bar-centered positions to the group-centered positions, and restoring the 'XDataMode' to 'auto' does not return the error bars to their original bar-centered positions. Additionally, the error bars of the incorrect figure also have their 'XDataMode' set to manual, leading me to think that the figure saving-and-reopening process somehow sets the 'XDataMode' to 'auto' and then back to 'manual', causing the error bars to lose their bar-centered positions. I have no idea how to prevent this.

Answer 1

[Adam Danz]

The problem is caused by assigning numeric x-values to the errorbars on a categorical x-axis. The errorbar function works around the difference in axis ruler types but when the figure is generated again by opening the figure the x-values of the errorbars are assigned to the categorical x-values.

In fact, if you look at the XData values of the errorbars after they are generated, their values are actually the categorical x-values. It's surprising the errorbars are positioned in the right place to begin with.

ebh =errorbar(x,barHeights,barErrors,'k','linestyle','none');

ebh.XData

ans =

1×3 categorical array

Group1 Group2 Group3

ans =

1×3 categorical array

Group1 Group2 Group3

ans =

1×3 categorical array

Group1 Group2 Group3

ans =

1×3 categorical array

Group1 Group2 Group3

ans =

1×3 categorical array

Group1 Group2 Group3

Instead of using a categorical x-ruler, use a numeric x-ruler and set the tick labels,

barHeights = [0.954, 0.666, 0.604, 0.842, 0.662;...
              0.021, 0.280, 0.259, 0.145, 0.212;...
              0.027, 0.075, 0.100, 0.022, 0.084];
barErrors = [0.023, 0.057, 0.091, 0.056, 0.081;...
             0.007, 0.046, 0.080, 0.053, 0.091;...
             0.018, 0.029, 0.029, 0.016, 0.034];
[nGroups,nBars] = size(barHeights);
%groupNames = categorical("Group" + string(1:nGroups));
barNames = "Bar" + string(1:nBars);
figure;
hold on
b = bar(barHeights,'FaceColor','flat'); % REMOVE THE CATEGORICAL X-VALUES
title("Title");
xlabel("xlabel");
ylabel("ylabel");
grid on;
x = reshape([b.XEndPoints],[nGroups,nBars]);
errorbar(x,barHeights,barErrors,'k','linestyle','none');

% SET THE TICKS AND TICKLABELS
set(gca, 'XTick', b(1).XData, 'XTickLabel', "Group" + string(1:nGroups)) 

legend(barNames);
hold off

If you're using a MATLAB release prior to R2019b, compute x using x=b(1).XData'+[b.XOffset];

[Andrew Soltisz]

SOLVED! I was really going into the weeds with this one. Great catch! Thank you!

[Samy Alkhayat]

Hello Adam,

I have the same issue, I know your code works on MATLAB 2019 and later, but I have 2018 version.

It seems I need a replacement for

x = reshape([b.XEndPoints],[nGroups,nBars]);

in MATLAB 2018, any tips?

Thanks in advance!

[Adam Danz]

This answer should point you in the right direction

https://www.mathworks.com/matlabcentral/answers/500168-add-error-bars-in-bar-graph#answer_410111

Specifically,

x = b(1).XData'+[b.XOffset];