matplotlib.units

The classes here provide support for using custom classes with Matplotlib, e.g., those that do not expose the array interface but know how to convert themselves to arrays. It also supports classes with units and units conversion. Use cases include converters for custom objects, e.g., a list of datetime objects, as well as for objects that are unit aware. We don’t assume any particular units implementation; rather a units implementation must register with the Registry converter dictionary and provide a ConversionInterface. For example, here is a complete implementation which supports plotting with native datetime objects:

import matplotlib.units as units
import matplotlib.dates as dates
import matplotlib.ticker as ticker
import datetime

class DateConverter(units.ConversionInterface):

    @staticmethod
    def convert(value, unit, axis):
        "Convert a datetime value to a scalar or array."
        return dates.date2num(value)

    @staticmethod
    def axisinfo(unit, axis):
        "Return major and minor tick locators and formatters."
        if unit != 'date':
            return None
        majloc = dates.AutoDateLocator()
        majfmt = dates.AutoDateFormatter(majloc)
        return units.AxisInfo(majloc=majloc, majfmt=majfmt, label='date')

    @staticmethod
    def default_units(x, axis):
        "Return the default unit for x or None."
        return 'date'

# Finally we register our object type with the Matplotlib units registry.
units.registry[datetime.date] = DateConverter()