>>> """
==========
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 that Matplotlib is entirely agnostic
to what kind of units client packages use.
"""
... 
... import numpy as np
... 
... import matplotlib.units as units
... import matplotlib.ticker as ticker
... import matplotlib.pyplot as plt
... 
... 
... class Foo:
...     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(units.ConversionInterface):
...     @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 np.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 np.iterable(x):
...             for thisx in x:
...                 return thisx.unit
...         else:
...             return x.unit
... 
... 
... units.registry[Foo] = FooConverter()
... 
... # create some Foos
... x = [Foo(val, 1.0) for val in range(0, 50, 2)]
... # and some arbitrary y data
... y = [i for i in range(len(x))]
... 
... fig, (ax1, ax2) = plt.subplots(1, 2)
... fig.suptitle("Custom units")
... fig.subplots_adjust(bottom=0.2)
... 
... # plot specifying units
... ax2.plot(x, y, 'o', xunits=2.0)
... ax2.set_title("xunits = 2.0")
... plt.setp(ax2.get_xticklabels(), rotation=30, ha='right')
... 
... # plot without specifying units; will use the None branch for axisinfo
... ax1.plot(x, y)  # uses default units
... ax1.set_title('default units')
... plt.setp(ax1.get_xticklabels(), rotation=30, ha='right')
... 
... plt.show()
...