.. note::
    :class: sphx-glr-download-link-note

    Click :ref:`here <sphx_glr_download_gallery_units_evans_test.py>` to download the full example code
.. rst-class:: sphx-glr-example-title

.. _sphx_glr_gallery_units_evans_test.py:


==========
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.




.. image:: /gallery/units/images/sphx_glr_evans_test_001.png
    :class: sphx-glr-single-img





.. code-block:: python


    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))]


    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()


.. _sphx_glr_download_gallery_units_evans_test.py:


.. only :: html

 .. container:: sphx-glr-footer
    :class: sphx-glr-footer-example



  .. container:: sphx-glr-download

     :download:`Download Python source code: evans_test.py <evans_test.py>`



  .. container:: sphx-glr-download

     :download:`Download Jupyter notebook: evans_test.ipynb <evans_test.ipynb>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    Keywords: matplotlib code example, codex, python plot, pyplot
    `Gallery generated by Sphinx-Gallery
    <https://sphinx-gallery.readthedocs.io>`_
