def percentile(self, n, default=None):
return numpy.asscalar(numpy.percentile(self.values, n)) if self.values else default<EOL>
Calculate the Nth Percentile value over the time series.

:param int n: Integer value of the percentile to calculate.
:param default: Value to return as a default should the calculation not be possible.
:return: Float representing the Nth percentile value or `None`.