Plot multiple errorbars in pairs

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Nikolas Spiliopoulos
Nikolas Spiliopoulos on 24 Sep 2019
Edited: Adam Danz on 10 Dec 2021
Hi again,
I have plotted some errorbars using the commands you suggested in my previous question:
x=1; y=8.35;
sd=4.13;
bar(x,y);
hold on
errorbar(x,y,sd)
ylim([0 14])
xticks([0:2])
hold off
However, I am trying to do the same with a pair of graphs, so in each number there are two bars instead of 1. I modified the code like this:
error=[3.3 2.1;1.1 4];
x=[1:2 ;1:2]';
y=[3.5 2.2; 5.2 3.3];
bar(x,y)
hold on
errorbar(x,y,error,'*')
ylim([-8 18])
xticks([1:2])
hold off
The problem is that the error bars which show the deviation don't fit exactly at the barcharts. Do you know how to fix this?
I have attached a screenshot

Accepted Answer

Adam Danz
Adam Danz on 24 Sep 2019
Edited: Adam Danz on 10 Dec 2021
To locate the center of each grouped bar in Matlab releases prior to R2019b, use the undocumented bar object property, "XOffset" which is the horizontal offset of each bar-center from the group index value. In R2019b and later, use XEndpoints.
xCnt are the bar centers.
error=[3.3 2.1;1.1 4];
x=[1:2 ;1:2]';
y=[3.5 2.2; 5.2 3.3];
h = bar(x,y)
hold on
% Get bar centers
xCnt = h(1).XData.' + [h.XOffset];
% Alternative: xCnt = get(h(1),'XData').' + cell2mat(get(h,'XOffset')).'; % XOffset is undocumented
% In Matlab R2019b and later,
% xCnt = vertcat(h.XEndPoints)';
errorbar(xCnt(:),y(:),error(:),'*') % <--- If you want 1 errorbar object
% errorbar(xCnt,y,error,'*') % <--- If you want separate errorbar objects, 1 for each bar-group
% errorbar(...,'k*') to make the errorbars black (which is better than yellow)
ylim([-8 18])
xticks([1:2])
hold off

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