How to make errorbar transparent?

How can I make a plot with discrete errorbar points which are transparent?

This thread did not contain an answer: https://www.mathworks.com/matlabcentral/answers/381188-how-to-define-transparency-of-errorbar

[Adam Danz]

The errorbar objects do not have an alpha property and they do not respond to adding an alpha value in the 4th position of the RGB color vector which is an undocumented feature in other graphics objects.

This answer by Tom Lane has 14 votes which suggests it has helped people in the past but it provides shaded error regions rather than error bars. Another FEX alternative here.

[supernoob]

Thanks. I need it to work for discrete errorbars, so unfortunately that other solution won't help me.

Thanks though!

[Adam Danz]

Here's an alternative that will take a little work. You could create a function that has the same inputs as errorbar(). In that function you can create vertical lines that span from the lower to upper error limits for each point. That you're dealing with line objects and you'll be able to control their alpha values by adding an alpha value to the 4th position of the RGB color value.

h = plot(); 
h.Color = [h.Color, 0.5]; % for 50% transparency

[Gino Delfe]

it works for plot, but not when you use it on the function errorbar()

Answer 1

[Adam Danz]

Unlike many line plots, the color property cannot be used to set transparency in errorbar().

Transparency can be set from within the hidden Bar and Line objects that represent the errorbars and trend line, respectively.

% Plot errorbars
cla
hold on
plot(rand(20),rand(20)*2-.5, 'yo', 'MarkerFaceColor', 'k', 'MarkerSize', 15, 'LineWidth', 1.5);
h = errorbar(linspace(0,1,5), linspace(0,1,5), .5*ones(1,5), 'r', 'LineWidth', 10);

% Set transparency level (0:1)
alpha = 0.65;   
% Set transparency (undocumented)
set([h.Bar, h.Line], 'ColorType', 'truecoloralpha', 'ColorData', [h.Line.ColorData(1:3); 255*alpha])

[David Saidman]

This worked.

The end caps on the errorbar were still solid, but I was able to make them transparent with other undocumented properties in the errorbar object. In case someone else may be trying to do the same thing:

The hidden properties h.CapH and h.MarkerHandle can be adjusted the same way as h.Line and h.Bar as above, but use FaceColorData & FaceColorType and EdgeColorData & EdgeColorType properties in place of ColorData & ColorType (or can be set to 'visible','off').

[Adam Danz]

Thanks for the addition, @David Saidman.

Unless there's something I'm missing, the FaceColor does not need changed for the caps. The transparency can be set in the EdgeColorData and EdgeColorType of the Cap handle.

set(h.Cap, 'EdgeColorType', 'truecoloralpha', 'EdgeColorData', [h.Cap.EdgeColorData(1:3); 255*alpha])