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Control errorbar width in Matlab R2014b

Asked by Sandor Toth on 11 Dec 2014
Latest activity Commented on by Brandon Madsen on 25 Jan 2018
Pre R2014b Matlab versions allowed the separate control of the length of the top and bottom error bar lines separately through the 'xdata' property. This is not possible any more in Matlab R2014b, where the 'xdata' property contains only the x coordinates of the data points but not the error bar lines. Is there a way to control the error bar line length in Matlab R2014b?

  8 Comments

It was possible in versions before R2014b. And I stuck with the same problem...
I've made a temporary solution to the problem by avoiding using the original "errorbar" function, and writing my own "terrorbar.m" that just draws the lines (using plot) as required.
It has the kinds of features needed by that those of us who might care about the width of our confidence intervals, i.e., you can specific the width in absolute terms (e.g. 'centi', 'inches') or normalised to the size of the figure ('norm') or to the units ('units').
It copes with changes in figure size, but not necessarily other changes (units, axis size), unless you re-call the function after (no parameters required). This is not ideal, but it's about as good as you'll get without hacking into the darkest depths of Matlab!
See 1/25/2018 answer here ( https://www.mathworks.com/matlabcentral/answers/100333-how-do-i-change-the-width-of-the-horizontal-lines-at-top-and-bottom-of-error-bars-in-my-errorbar-plo ) for a version that I think should work for 2014b (it works for 2015b for sure). It involves hacking into the darkest depths of Matlab, as suspected ;)

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3 Answers

Answer by Sean de Wolski
on 7 Jan 2015

Pre-R2014b, this was possible because the errorbar series had children which were lines you could adjust. Since that's no longer the case, this approach no longer works.
I'd at least recommend contacting tech-support with your use-case and reasoning so that they can add an enhancement request for it.

  5 Comments

Any news regarding this high priority enhancement? I have a problem this workaround doesn't solve. The crossbars are too wide, and overlap the neighboring bars. This workaround actually makes the problem worse, since the crossbar width is a fixed % of the total horizontal range of the data, regardless of the number of bars.
I replied to my Mathworks support case on this (2 years old) 4 days ago. No reply yet. I'll update here if I get an answer.
I received a response from MathWorks. A CapSize property has been added to the errorbars as of R2016b. Here is my previous example updated to use this functionality (with excessive crossbar width):
x=[5 25];
y=[10 10];
err=[5 5];
hold on
h=errorbar(x,y,err,'ro');
h.CapSize = 12;
x=[13 17];
h=errorbar(x,y,err,'bo');
h.CapSize = 12;
print('-dpng','errorbars3.png');
The resultant plot is as follows.
However, I also noticed that the errorbar width was actually ok for this example in R2016b before I even adjusted the capsize, so it seems that some other general improvements were made as well.
Finally, MathWorks also provided the following code example for manually drawing the crossbars in case you don't have R2016b.
% Create errorbar
X = 0:pi/10:pi;
Y = sin(X) + 1;
E = std(Y) * ones(size(X));
ha = errorbar(X, Y, E);
% Width of the top and bottom lines of errorbar
xlength = 0.1;
% Make horizontal lines with 'line'
for k = 1:length(X)
x = [X(k) - xlength, X(k) + xlength];
y_h = [Y(k) + E(k), Y(k) + E(k)];
line(x, y_h);
y_b = [Y(k) - E(k), Y(k) - E(k)];
line(x, y_b);
end

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Answer by Ramaprasad Kulkarni on 20 Dec 2016

You guys might have found a solution, but just putting this out there:
An alternate and easier option to control the width of the top/bottom crossbars is to plot each pair of [x(i), y(i)] points and corresponding errorbar(x(i),y(i),err(i)). This ensures the width of the top/bottom crossbars is 0.02*x(i).
The downside of this approach is you have to use an unnecessary for loop to go over all the values in the X/Y vectors.

  1 Comment

Wouldn't that result in inconsistent crossbar widths though, if they were scaled with the x position value?

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