CODEWITHSUNDEEP
pythonmatplotlib
pwuertz
pwuertz

Reputation: 1325

Duplicate Tick Labels in Matplotlib

I'm searching for a way to extract all text elements from a matplotlibfigure including their position, style, alignment etc. Calling the findobj(matplotlib.text.Text) method of a figure does that job exactly. However, I get some weird duplicates for all the tick labels and I don't know how to handle them.

For example, use findobj for printing all Text elements of an axis:

import matplotlib
import pylab as p

p.plot([1,2,3])
p.xticks([1],["tick"])
ax = p.gca()
fig = p.gcf()

p.draw()
def print_texts(artist):
    for t in artist.findobj(matplotlib.text.Text):
        if t.get_visible() and t.get_text():
            print " %r @ %s" % (t.get_text(), t.get_position())

print "X-Axis Text Elements:"
print_texts(ax.xaxis)
print "Y-Axis Text Elements:"
print_texts(ax.yaxis)

Result:

X-Axis Text Elements:
 'tick' @ (1.0, 0.0)
 'tick' @ (0.0, 1.0)
Y-Axis Text Elements:
 u'1.0' @ (0.0, 1.0)
 u'1.0' @ (1.0, 0.0)
 u'1.5' @ (0.0, 1.5)
 u'1.5' @ (1.0, 0.0)
 u'2.0' @ (0.0, 2.0)
 u'2.0' @ (1.0, 0.0)
 u'2.5' @ (0.0, 2.5)
 u'2.5' @ (1.0, 0.0)
 u'3.0' @ (0.0, 3.0)
 u'3.0' @ (1.0, 0.0)

Note that all tick labels have duplicates positioned at the end of the axis. Why? How to filter them out from a list of Text elements? Their get_visible() attribute is True.

Another thing is that I first have to do call draw() in order to update/generate the ticks. How do I force an update of the tick labels? matplotlib.colorbar.Colorbar seems to have a update_ticks() method, but I can't find something similar for ticks on the axes.

I also tried writing a custum backend and fetch all the texts from the draw_text() method of the renderer. In contrast to the documentation draw_text() does not receive a matplotlib.text.Text instance with all the necessary information but only a simple string and a pre-layouted position.

Upvotes: 2

Views: 3134

Answers (1)

pwuertz
pwuertz

Reputation: 1325

The answer to this problem was given in the matplotlib mailing list. The Tick object always creates two text labels, one for the left/bottom and one for the right/top. When a Tick artist is drawn its label1On and label2On attributes define which of the two child text labels receive the draw() call. Both of them remain in the visible state however.

So before iterating through all the text elements of a figure, I hide those labels that are not supposed to be seen:

for tick in fig.findobj(matplotlib.axis.Tick):
    tick.label1.set_visible(tick.label1On)
    tick.label2.set_visible(tick.label2On)

for text in fig.findobj(match=Text, include_self=False):
    s = text.get_text()
    if not s or not text.get_visible(): continue
    # do something with the texts

Upvotes: 1

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