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Merge pull request #5785 from anntzer/better-offsettext-choice
Better choice of offset-text.
1 parent f82fc3b commit beb08c8

3 files changed

Lines changed: 90 additions & 19 deletions

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‎doc/users/whats_new/offset-text-choice.rst‎

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,6 @@
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Improved offset text choice
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---------------------------
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The default offset-text choice was changed to only use significant digits that
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are common to all ticks (e.g. 1231..1239 -> 1230, instead of 1231), except when
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they straddle a relatively large multiple of a power of ten, in which case that
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multiple is chosen (e.g. 1999..2001->2000).

‎lib/matplotlib/tests/test_ticker.py‎

Lines changed: 48 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
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from matplotlib.externals import six
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import nose.tools
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from nose.tools import assert_raises
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from nose.tools import assert_equal, assert_raises
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from numpy.testing import assert_almost_equal
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import numpy as np
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import matplotlib
@@ -159,6 +159,53 @@ def test_SymmetricalLogLocator_set_params():
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nose.tools.assert_equal(sym.numticks, 8)
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161161

162+
@cleanup
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def test_ScalarFormatter_offset_value():
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fig, ax = plt.subplots()
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formatter = ax.get_xaxis().get_major_formatter()
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def check_offset_for(left, right, offset):
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ax.set_xlim(left, right)
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# Update ticks.
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next(ax.get_xaxis().iter_ticks())
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assert_equal(formatter.offset, offset)
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test_data = [(123, 189, 0),
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(-189, -123, 0),
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(12341, 12349, 12340),
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(-12349, -12341, -12340),
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(99999.5, 100010.5, 100000),
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(-100010.5, -99999.5, -100000),
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(99990.5, 100000.5, 100000),
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(-100000.5, -99990.5, -100000),
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(1233999, 1234001, 1234000),
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(-1234001, -1233999, -1234000),
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(1, 1, 1),
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(123, 123, 120),
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# Test cases courtesy of @WeatherGod
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(.4538, .4578, .45),
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(3789.12, 3783.1, 3780),
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(45124.3, 45831.75, 45000),
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(0.000721, 0.0007243, 0.00072),
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(12592.82, 12591.43, 12590),
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(9., 12., 0),
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(900., 1200., 0),
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(1900., 1200., 0),
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(0.99, 1.01, 1),
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(9.99, 10.01, 10),
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(99.99, 100.01, 100),
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(5.99, 6.01, 6),
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(15.99, 16.01, 16),
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(-0.452, 0.492, 0),
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(-0.492, 0.492, 0),
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(12331.4, 12350.5, 12300),
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(-12335.3, 12335.3, 0)]
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for left, right, offset in test_data:
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yield check_offset_for, left, right, offset
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yield check_offset_for, right, left, offset
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def _logfe_helper(formatter, base, locs, i, expected_result):
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vals = base**locs
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labels = [formatter(x, pos) for (x, pos) in zip(vals, i)]

‎lib/matplotlib/ticker.py‎

Lines changed: 36 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -159,6 +159,7 @@
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from matplotlib.externals import six
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import decimal
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import itertools
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import locale
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import math
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import numpy as np
@@ -635,33 +636,50 @@ def set_locs(self, locs):
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vmin, vmax = self.axis.get_view_interval()
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d = abs(vmax - vmin)
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if self._useOffset:
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self._set_offset(d)
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self._compute_offset()
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self._set_orderOfMagnitude(d)
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self._set_format(vmin, vmax)
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def _set_offset(self, range):
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# offset of 20,001 is 20,000, for example
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def _compute_offset(self):
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locs = self.locs
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if locs is None or not len(locs) or range == 0:
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if locs is None or not len(locs):
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self.offset = 0
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return
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# Restrict to visible ticks.
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vmin, vmax = sorted(self.axis.get_view_interval())
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locs = np.asarray(locs)
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locs = locs[(vmin <= locs) & (locs <= vmax)]
652-
ave_loc = np.mean(locs)
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if len(locs) and ave_loc: # dont want to take log10(0)
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ave_oom = math.floor(math.log10(np.mean(np.absolute(locs))))
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range_oom = math.floor(math.log10(range))
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if np.absolute(ave_oom - range_oom) >= 3: # four sig-figs
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p10 = 10 ** range_oom
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if ave_loc < 0:
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self.offset = (math.ceil(np.max(locs) / p10) * p10)
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else:
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self.offset = (math.floor(np.min(locs) / p10) * p10)
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else:
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self.offset = 0
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if not len(locs):
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self.offset = 0
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return
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lmin, lmax = locs.min(), locs.max()
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# Only use offset if there are at least two ticks and every tick has
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# the same sign.
658+
if lmin == lmax or lmin <= 0 <= lmax:
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self.offset = 0
660+
return
661+
# min, max comparing absolute values (we want division to round towards
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# zero so we work on absolute values).
663+
abs_min, abs_max = sorted([abs(float(lmin)), abs(float(lmax))])
664+
sign = math.copysign(1, lmin)
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# What is the smallest power of ten such that abs_min and abs_max are
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# equal up to that precision?
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# Note: Internally using oom instead of 10 ** oom avoids some numerical
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# accuracy issues.
669+
oom_max = math.ceil(math.log10(abs_max))
670+
oom = 1 + next(oom for oom in itertools.count(oom_max, -1)
671+
if abs_min // 10 ** oom != abs_max // 10 ** oom)
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if (abs_max - abs_min) / 10 ** oom <= 1e-2:
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# Handle the case of straddling a multiple of a large power of ten
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# (relative to the span).
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# What is the smallest power of ten such that abs_min and abs_max
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# are no more than 1 apart at that precision?
677+
oom = 1 + next(oom for oom in itertools.count(oom_max, -1)
678+
if abs_max // 10 ** oom - abs_min // 10 ** oom > 1)
679+
# Only use offset if it saves at least two significant digits.
680+
self.offset = (sign * (abs_max // 10 ** oom) * 10 ** oom
681+
if abs_max // 10 ** oom >= 10
682+
else 0)
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666684
def _set_orderOfMagnitude(self, range):
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# if scientific notation is to be used, find the appropriate exponent

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