Multiple lines for a single legend entry

Hi!

I was wondering if it is possible to add a single legend for multiple lines, like here:

https://matplotlib.org/3.2.1/gallery/text_labels_and_annotations/legend_demo.html

Thank you in advance!

[darova]

I think it's impossible. One object - one legend

Answer 1

[David Neussl]

Hi, i think i may have a solution for your problem. My approach was to "plot" invisible NaNs, give them the color i want and create legend entries for those NaNs.

For example: Lets say we have 6 lines (10 data points each), where the first 3 are of GROUP 1 and the last three are of GROUP 2:

data = rand(10,6);
cm = colormap('lines'); % Get default line colors

figure, hold on;
for i = 1:6
  % Get index for line colors (GROUP1=1:3, GROUP2=4:6)
  if i <= 3
    colorindex = 1;
  else
    colorindex = 2;
  end
  % Turn HandleVisibility off to disable legend entries for these lines
  plot(data(:,i), 'Color', cm(colorindex,:), 'HandleVisibility', 'off');
end

% These nans will be invisible
plot(NaN, 'DisplayName', 'GROUP 1', 'Color', cm(1,:));
plot(NaN, 'DisplayName', 'GROUP 2', 'Color', cm(2,:));

% Show legend
legend('Location', 'Best');

This then gives this plot as a result

[Szilard Novoth]

That is a clever workaround, thank you :)

The perfect solution would be, if I could give a single legend for two (or more) different lines.

For example you have 3 red lines, but maybe I want to differentiate these lines by having one dashed and another one dotted, but still only have the legend GROUP 1

Like:

red ‘-‘, ‘:’, ‘.’ GROUP1

blue ‘-‘, ‘:’, ‘.’ GROUP2