8000 ENH: Added percent formatter and tests · arunkgupta/matplotlib@0e35e6b · GitHub
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ENH: Added percent formatter and tests
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‎doc/users/whats_new/percent_formatter.rst

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Added `matplotlib.ticker.PercentFormatter`
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------------------------------------------
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The new formatter has some nice features like being able to convert from
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arbitrary data scales to percents, a customizable percent symbol and
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either automatic or manual control over the decimal points.

‎lib/matplotlib/tests/test_ticker.py

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@@ -366,6 +366,39 @@ def test_formatstrformatter():
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tmp_form = mticker.StrMethodFormatter('{x:05d}')
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nose.tools.assert_equal('00002', tmp_form(2))
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def _percent_format_helper(xmax, decimals, symbol, x, display_range, expected):
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formatter = mticker.PercentFormatter(xmax, decimals, symbol)
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nose.tools.assert_equal(formatter.format_pct(x, display_range), expected)
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def test_percentformatter():
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test_cases = (
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# Check explicitly set decimals over different intervals and values
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(100, 0, '%', 120, 100, '120%'),
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(100, 0, '%', 100, 90, '100%'),
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(100, 0, '%', 90, 50, '90%'),
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(100, 0, '%', 1.7, 40, '2%'),
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(100, 1, '%', 90.0, 100, '90.0%'),
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(100, 1, '%', 80.1, 90, '80.1%'),
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(100, 1, '%', 70.23, 50, '70.2%'),
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# 60.554 instead of 60.55: see https://bugs.python.org/issue5118
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(100, 1, '%', 60.554, 40, '60.6%'),
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# Check auto decimals over different intervals and values
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(100, None, '%', 95, 1, '95.00%'),
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(1.0, None, '%', 3, 6, '300%'),
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(17.0, None, '%', 1, 8.5, '6%'),
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(17.0, None, '%', 1, 8.4, '5.9%'),
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(5, None, '%', -100, 0.000001, '-2000.00000%'),
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# Check percent symbol
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(1.0, 2, None, 1.2, 100, '120.00'),
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(75, 3, '', 50, 100, '66.667'),
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(42, None, '^^Foobar$$', 21, 12, '50.0^^Foobar$$'),
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)
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for case in test_cases:
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yield (_percent_format_helper,) + case
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if __name__ == '__main__':
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import nose
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nose.runmodule(argv=['-s', '--with-doctest'], exit=False)

‎lib/matplotlib/ticker.py

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@@ -131,6 +131,8 @@
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:class:`LogFormatter`
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formatter for log axes
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:class:`PercentFormatter`
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Format labels as a percentage
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You can derive your own formatter from the Formatter base class by
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simply overriding the ``__call__`` method. The formatter class has access
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import warnings
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__all__ = ('TickHelper', 'Formatter', 'FixedFormatter',
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'NullFormatter', 'FuncFormatter', 'FormatStrFormatter',
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'StrMethodFormatter', 'ScalarFormatter', 'LogFormatter',
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'LogFormatterExponent', 'LogFormatterMathtext',
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'LogitFormatter', 'EngFormatter', 'PercentFormatter',
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'Locator', 'IndexLocator', 'FixedLocator', 'NullLocator',
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'LinearLocator', 'LogLocator', 'AutoLocator',
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'MultipleLocator', 'MaxNLocator', 'AutoMinorLocator',
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'SymmetricalLogLocator')
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if six.PY3:
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long = int
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@@ -922,8 +936,10 @@ def __call__(self, x, pos=None):
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return self.fix_minus(s)
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def format_eng(self, num):
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""" Formats a number in engineering notation, appending a letter
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representing the power of 1000 of the original number. Some examples:
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"""
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Formats a number in engineering notation, appending a letter
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representing the power of 1000 of the original number.
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Some examples:
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>>> format_eng(0) # for self.places = 0
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'0'
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>>> format_eng("-1e-6") # for self.places = 2
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u'-1.00 \u03bc'
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@param num: the value to represent
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@type num: either a numeric value or a string that can be converted to
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a numeric value (as per decimal.Decimal constructor)
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@return: engineering formatted string
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`num` may be a numeric value or a string that can be converted
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to a numeric value with the `decimal.Decimal` constructor.
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"""
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dnum = decimal.Decimal(str(num))
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sign = 1
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return formatted.strip()
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class PercentFormatter(Formatter):
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"""
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Format numbers as a percentage.
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How the number is converted into a percentage is determined by the
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`xmax` parameter. `xmax` is the data value that corresponds to 100%.
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Percentages are computed as ``x / xmax * 100``. So if the data is
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already scaled to be percentages, `xmax` will be 100. Another common
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situation is where `xmax` is 1.0.
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`symbol` is a string which will be appended to the label. It may be
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`None` or empty to indicate that no symbol should be used.
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`decimals` is the number of decimal places to place after the point.
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If it is set to `None` (the default), the number will be computed
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automatically.
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"""
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def __init__(self, xmax=100, decimals=None, symbol='%'):
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self.xmax = xmax + 0.0
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self.decimals = decimals
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self.symbol = symbol
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def __call__(self, x, pos=None):
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"""
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Formats the tick as a percentage with the appropriate scaling.
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"""
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ax_min, ax_max = self.axis.get_view_interval()
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display_range = abs(ax_max - ax_min)
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return self.fix_minus(self.format_pct(x, display_range))
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def format_pct(self, x, display_range):
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"""
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Formats the number as a percentage number with the correct
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number of decimals and adds the percent symbol, if any.
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If `self.decimals` is `None`, the number of digits after the
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decimal point is set based on the `display_range` of the axis
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as follows:
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+---------------+----------+------------------------+
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| display_range | decimals | sample |
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+---------------+----------+------------------------+
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| >50 | 0 | ``x = 34.5`` => 35% |
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+---------------+----------+------------------------+
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| >5 | 1 | ``x = 34.5`` => 34.5% |
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+---------------+----------+------------------------+
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| >0.5 | 2 | ``x = 34.5`` => 34.50% |
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+---------------+----------+------------------------+
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| ... | ... | ... |
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+---------------+----------+------------------------+
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This method will not be very good for tiny axis ranges or
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extremely large ones. It assumes that the values on the chart
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are percentages displayed on a reasonable scale.
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"""
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x = self.convert_to_pct(x)
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if self.decimals is None:
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# conversion works because display_range is a difference
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scaled_range = self.convert_to_pct(display_range)
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if scaled_range <= 0:
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decimals = 0
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else:
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# Luckily Python's built-in ceil rounds to +inf, not away from
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# zero. This is very important since the equation for decimals
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# starts out as `scaled_range > 0.5 * 10**(2 - decimals)`
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# and ends up with `decimals > 2 - log10(2 * scaled_range)`.
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decimals = math.ceil(2.0 - math.log10(2.0 * scaled_range))
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if decimals > 5:
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decimals = 5
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elif decimals < 0:
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decimals = 0
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else:
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decimals = self.decimals
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s = '{x:0.{decimals}f}'.format(x=x, decimals=int(decimals))
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if self.symbol:
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return s + self.symbol
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return s
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def convert_to_pct(self, x):
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return 100.0 * (x / self.xmax)
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class Locator(TickHelper):
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"""
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Determine the tick locations;
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locator = MultipleLocator(ticksize)
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return locator
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__all__ = ('TickHelper', 'Formatter', 'FixedFormatter',
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'NullFormatter', 'FuncFormatter', 'FormatStrFormatter',
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'StrMethodFormatter', 'ScalarFormatter', 'LogFormatter',
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'LogFormatterExponent', 'LogFormatterMathtext', 'Locator',
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'IndexLocator', 'FixedLocator', 'NullLocator',
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'LinearLocator', 'LogLocator', 'AutoLocator',
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'MultipleLocator', 3E9D 'MaxNLocator', 'AutoMinorLocator',
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'SymmetricalLogLocator')

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