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'''Dumping ground for VOLTTRON platform™ agent math helper functions.
Not meant to replace numpy in all cases. A basic set common math
routines to remove the need for numpy in simple cases.
This module should NEVER import numpy as that would defeat the
purpose.'''
[docs]def mean(data):
"""Return the sample arithmetic mean of data."""
n = len(data)
if n < 1:
raise ValueError('mean requires at least one data point')
return sum(data)/n # in Python 2 use sum(data)/float(n)
def _ss(data):
"""Return sum of square deviations of sequence data."""
c = mean(data)
ss = sum((x-c)**2 for x in data)
return ss
[docs]def pstdev(data):
"""Calculates the population standard deviation."""
n = len(data)
if n < 2:
raise ValueError('variance requires at least two data points')
ss = _ss(data)
pvar = ss/n # the population variance
return pvar**0.5
[docs]def stdev(data):
"""Calculates the sample standard deviation."""
n = len(data)
if n < 2:
raise ValueError('variance requires at least two data points')
ss = _ss(data)
pvar = ss/(n-1) # sample variance
return pvar**0.5