Source code for spynnaker.pyNN.utilities.running_stats

# Copyright (c) 2017-2019 The University of Manchester
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import math


[docs]class RunningStats(object): """ Keeps running statistics. From: http://www.johndcook.com/blog/skewness_kurtosis/ """ __slots__ = ["__mean", "__mean_2", "__n_items"] def __init__(self): self.__mean = 0.0 self.__mean_2 = 0.0 self.__n_items = 0
[docs] def add_item(self, x): """ Adds an item to the running statistics. :param x: The item to add :type x: int or float """ old_n_items = self.__n_items self.__n_items += 1 delta = x - self.__mean delta_n = delta / self.__n_items term_1 = delta * delta_n * old_n_items self.__mean += delta_n self.__mean_2 += term_1
[docs] def add_items(self, mean, variance, n_items): """ Add a bunch of items (via their statistics). :param float mean: The mean of the items to add. :param float variance: The variance of the items to add. :param int n_items: The number of items represented. """ if n_items > 0: new_n_items = self.__n_items + n_items mean_2 = variance * (n_items - 1.0) delta = mean - self.__mean delta_2 = delta * delta new_mean = (((self.__n_items * self.__mean) + (n_items * mean)) / new_n_items) new_mean_2 = (self.__mean_2 + mean_2 + (delta_2 * self.__n_items * n_items) / new_n_items) self.__n_items = new_n_items self.__mean = new_mean self.__mean_2 = new_mean_2
@property def n_items(self): """ The number of items seen. :rtype: int """ return self.__n_items @property def mean(self): """ The mean of the items seen. :rtype: float """ return self.__mean @property def variance(self): """ The variance of the items seen. :rtype: float """ if self.__n_items <= 1: return 0.0 return self.__mean_2 / (self.__n_items - 1.0) @property def standard_deviation(self): """ The population standard deviation of the items seen. :rtype: float """ return math.sqrt(self.variance)