matplotlib legend problem

[John Hunter]

>>>>> "bwaha" == bwaha  <cfriedl at bigpond.net.au> writes:
    bwaha> added the location argument. Finally realised it was due to
    bwaha> having a default of 'best' location in my code which meant
    bwaha> it went searching for intersection with lines that don't
    bwaha> exist (outside of the LineCollection). So I disabled the
    bwaha> 'best' location option. Then I figured, since I'd cleaned
    bwaha> up my code a bit, I'd reinstate my earlier pylab.plot based
    bwaha> line drawing code to see if the clean up made any
    bwaha> difference to what was previously abysmal performance. The
    bwaha> lines plotted faster than the LineCollection code! When I
    bwaha> removed the legend hack for LineCollections there was
    bwaha> virtually no difference. (Story is not finshed yet). So I
    bwaha> figured after all that that I'd reinstate my pylab.plot
    bwaha> based code since I could plot a greater range of symbols
    bwaha> than with LineCollections with no speed loss. And I thought
    bwaha> why not go the whole hog and reinstate the 'best' location
    bwaha> option too. Boom! Plotting performance was abysmal
    bwaha> again. Finally I realised that enabling 'best' and having
    bwaha> it as the default meant that as I added new data to plot,
    bwaha> the search time for a good place to put the legend
    bwaha> increased dramtically, and probably became more difficult
    bwaha> with more and more lines filling the canvas.

    bwaha> Anyway now I'm a lot happier than when I started because
    bwaha> I've retained my original range of plot styles and I got
    bwaha> much faster plotting. Hopefully this lesson can help
    bwaha> someone else.


Sorry you had to find this out after so much trial and error.  For a
small number of large length lines (eg 10 at 30k points each), plot
will be much faster than line collections as you observed.  For a
large number of small lines (eg 1000 at 20 points each) line
collections will be much faster.  And yes, the "best" optimization for
the legend is slow -- I'm on the fence as to whether this should be
the default or not.  At least clearly flagging this as a performance
bottleneck in the docs would be useful.

Cheers,
JDH