'Convenience constructor for passing `decay_rate` in terms of center of
mass.
Forwards `decay_rate` as `1 - (1 / 1 + center_of_mass)`.  This provides
behavior equivalent to passing `center_of_mass` to pandas.ewma.
Examples
.. code-block:: python
# Equivalent to:
# my_ewma = EWMA(
#    inputs=[USEquityPricing.close],
#    window_length=30,
#    decay_rate=(1 - (1 / 15.0)),
my_ewma = EWMA.from_center_of_mass(
inputs=[USEquityPricing.close],
window_length=30,
center_of_mass=15,
Notes
This classmethod is provided by both
:class:`ExponentialWeightedMovingAverage` and
:class:`ExponentialWeightedMovingStdDev`.'

@classmethod
def from_center_of_mass(cls, inputs, window_length, center_of_mass, **kwargs):

    return cls(inputs=inputs, window_length=window_length, decay_rate=(1.0 - (1.0 / (1.0 + center_of_mass))), **kwargs)
