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Evans test

A mockup “Foo” units class which supports conversion and different tick formatting depending on the “unit”. Here the “unit” is just a scalar conversion factor, but this example shows mpl is entirely agnostic to what kind of units client packages use.

../../_images/sphx_glr_evans_test_001.png
from matplotlib.cbook import iterable
import matplotlib.units as units
import matplotlib.ticker as ticker
import matplotlib.pyplot as plt


class Foo(object):
    def __init__(self, val, unit=1.0):
        self.unit = unit
        self._val = val * unit

    def value(self, unit):
        if unit is None:
            unit = self.unit
        return self._val / unit


class FooConverter(object):
    @staticmethod
    def axisinfo(unit, axis):
        'return the Foo AxisInfo'
        if unit == 1.0 or unit == 2.0:
            return units.AxisInfo(
                majloc=ticker.IndexLocator(8, 0),
                majfmt=ticker.FormatStrFormatter("VAL: %s"),
                label='foo',
                )

        else:
            return None

    @staticmethod
    def convert(obj, unit, axis):
        """
        convert obj using unit.  If obj is a sequence, return the
        converted sequence
        """
        if units.ConversionInterface.is_numlike(obj):
            return obj

        if iterable(obj):
            return [o.value(unit) for o in obj]
        else:
            return obj.value(unit)

    @staticmethod
    def default_units(x, axis):
        'return the default unit for x or None'
        if iterable(x):
            for thisx in x:
                return thisx.unit
        else:
            return x.unit


units.registry[Foo] = FooConverter()

# create some Foos
x = []
for val in range(0, 50, 2):
    x.append(Foo(val, 1.0))

# and some arbitrary y data
y = [i for i in range(len(x))]


# plot specifying units
fig = plt.figure()
fig.suptitle("Custom units")
fig.subplots_adjust(bottom=0.2)
ax = fig.add_subplot(1, 2, 2)
ax.plot(x, y, 'o', xunits=2.0)
for label in ax.get_xticklabels():
    label.set_rotation(30)
    label.set_ha('right')
ax.set_title("xunits = 2.0")


# plot without specifying units; will use the None branch for axisinfo
ax = fig.add_subplot(1, 2, 1)
ax.plot(x, y)  # uses default units
ax.set_title('default units')
for label in ax.get_xticklabels():
    label.set_rotation(30)
    label.set_ha('right')

plt.show()

Total running time of the script: ( 0 minutes 0.038 seconds)

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