Creating a Legend for a Boxplot with Two Colors

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Hi, I need help inserting a legend for a boxplot with two colors (red & blue). My code for this is:
boxplot(data, 'notch', 'on', 'symbol', '*','colors','rb');
legend('Label1','Label2');
But I get no legend and it says "Warning: Plot empty" in the command window. Any help on this matter would be much appreciated. Thank you.

Accepted Answer

Walter Roberson
Walter Roberson on 28 Jun 2011
It isn't a bug. The annotations for the boxes have their IconDisplayStyle property set 'off' which is a signal that they are not to be included in legends.
You can include them deliberately by using
legend(findobj(gca,'Tag','Box'),'Label1','Label2')
but note that the boxes all have the same color (at least with the call you use) so the legend lines will be in the same color as each other.
  5 Comments
Isabel Chen
Isabel Chen on 15 Jun 2016
I am using Matlab 2016a, and with the code above, I get the following error message:
Warning: Ignoring extra legend entries.
> In legend>set_children_and_strings (line 643)
In legend>make_legend (line 328)
In legend (line 257)
The plot looks fine, apart from the legend entries in the wrong order. Any ideas?
Walter Roberson
Walter Roberson on 16 Jun 2016
In your line similar to
legend(findobj(gca,'Tag','Box'),'Label1','Label2')
you need to supply as many labels as you have columns in your data. boxplot creates one object with tag Box for each column of data.

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More Answers (1)

Oleg Komarov
Oleg Komarov on 28 Jun 2011
Use the option labels, dunno if it is a bug but legend doesn't seem to work.

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