Paul Ivanov, on 2011-02-01 17:14, wrote: > Kris Kuhlman, on 2011-02-01 18:03, wrote: > > I am trying to plot a large number of locations that need to be labeled. > > Often the locations are quite clustered and the resulting text is > > unreadable. I have been looking through the API and examples on the > > matplotlib web page, and I don't see a straightforward way to plot text > > labels, preventing them from overlapping. There is no easy answer to the > > problem, since locating the labels so they are close to the point you want > > to label, and not overlapping is a sort of optimization problem, I guess. > > > > Using annotate(), the location and alignment of the text can be fixed, but > > you don't know the size of the resulting box until after draw() is called. > > Once draw is called, you can inquire what the bounding box for a label is, > > and then check to see if it overlaps with other labels, but this is an > > iterative process, and draw() can be quite slow to call repeatedly. > > > > I guess unless you use a fixed-width font (possible, but not optimal), you > > just don't know how big the labels will be, and therefore where they will > > extend to, and then how they should be avoided. This involves coming up > > with some sort of accounting system for the location and size of each text > > box, outside of the matplotlib API, and seems sub-optimal. > > > > Has anybody dealt with this problem and come up with an elegant or efficient > > solution? > > Hi Kris, > > unfortunately, there isn't a turn-key solution implemented for > this at the moment, but this would be something very useful and > something I've been wanting to see in matplotlib, but never had a > strong enough need to implement myself. > > Take a look here for the type of machinery that could be used to > implement such functionality: > > http://matplotlib.sourceforge.net/faq/howto_faq.html#automatically-make-room-for-tick-labels
I should add that the overlaps and count_overlaps methods of
mpl.transforms.Bbox could be used for some sort of iterative
solution, as you can get the bounding box using
a = plt.annotate("Foo",(1,2))
bbox = a.get_window_extent()
Also, depeding on the number of labels and the need for reproducibility
of plots, you can just make the labels draggable, and move them
around using the mouse
a.draggable()
best,
--
Paul Ivanov
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http://pirsquared.org | GPG/PGP key id: 0x0F3E28F7
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