Re: [Matplotlib-users] Markers in legend?

[John H. <jdh...@ac...>]

>>>>> "Robert" == Robert Leftwich <ro...@le...> writes:

    Robert> Is it possible to include a marker from one or more
    Robert> scatter plots in the legend?  Robert

This is a bit tricky -- scatter plots can vary in size and color.
What should one use for the legend marker?  So the short answer is no.
My question for you is, "how *should* it work?"

Not if you are using homogeneous marker sizes and colors, I suggest
using plot markers tweaking the properties, as in

  line, = plot(x,y,linestyle='None', marker='s', 
               markerfacecolor='red', markeredgecolor='g',
               markersize=20, markeredgewith=3)


or the pithy

  line, = plot(x, y, ls='None', marker='s', 
               mfc='red', mec='g', ms=20,, mew=3)

These you can add to the legend.

  legend((line,), ('label',))

In matplotlib-0.72, this will be as fast or faster than scatter for
the agg backend.  Probably faster.

If this is not an option -- eg you need variation in size but not
color, you can use a line as a stand-in in your legend.  Create the
line, don't add it to the axes, but pass it to the legend

    sizes = 20*rand(len(x))
    scatter(x,y,s=sizes, marker='o', c='red')

    # now create the proxy line but don't add it to axes for drawing
    line = Line2D(x,y,marker='o', color='red')

    legend((line,), ('label',))


This is untested, so let me know how it goes...

JDH