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@giwa giwa/stat_basic.py
Last active Aug 29, 2015

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Set of basic statistic operations
# Set of basic statistics operations
#
import math
def median(items):
"""
Return median
if number of items is odd, return average of 2 middles.
>>> items = [10, 2, 5, 7, 4]
>>> median(items)
4
"""
num_items = len(items)
if num_items % 2 == 0:
return items[num_items - 1]
else:
m1 = items[int(num_items)]
m2 = items[int(num_items) + 1]
return (m1 + m2) / 2
def arithmetic_mean(items):
"""
Return arithmetic mean
>>> items = [10, 2, 5, 7, 4]
>>> arithmetic_mean(items)
5.6
"""
return reduce(lambda x, y: x + y, items) / float(len(items))
def sum_of_squares_deviation(items):
"""
Return sum of squares deviation
>>> items = [10, 2, 5, 7, 4]
>>> sum_of_squares_deviation(items)
37.2
"""
ave_items = arithmetic_mean(items)
deviation_of_items = map(lambda x: pow(x - ave_items, 2), items)
return reduce(lambda x, y: x + y, deviation_of_items)
def divergence(items):
"""
Return divergence
>>> items = [10, 2, 5, 7, 4]
>>> divergence(items)
9.3
"""
return sum_of_squares_deviation(items) / (len(items) - 1)
def standard_deviation(items):
"""
Return standard deviation
>>> items = [10, 2, 5, 7, 4]
>>> round(standard_deviation(items), 2)
3.05
"""
return math.sqrt(divergence(items))
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