常用统计类函数的python实现

包含了求和、计数、最大最小值、平均值、中位数、标准偏差、百分比等常用统计函数

#!/usr/bin/env python
#  corestats.py (COREy STATS)
#  Copyright (c) 2006-2007, Corey Goldberg (corey@goldb.org)
#
#    statistical calculation class
#    for processing numeric sequences
#
#  license: GNU LGPL
#
#  This library is free software; you can redistribute it and/or
#  modify it under the terms of the GNU Lesser General Public
#  License as published by the Free Software Foundation; either
#  version 2.1 of the License, or (at your option) any later version.
 
import sys
 
class Stats:
 
    def __init__(self, sequence):
        # sequence of numbers we will process
        # convert all items to floats for numerical processing
        self.sequence = [float(item) for item in sequence]
 
    def sum(self):
        if len(self.sequence) < 1:
            return None
        else:
            return sum(self.sequence)
 
    def count(self):
        return len(self.sequence)
 
    def min(self):
        if len(self.sequence) < 1:
            return None
        else:
            return min(self.sequence)
 
    def max(self):
        if len(self.sequence) < 1:
            return None
        else:
            return max(self.sequence)
 
    def avg(self):
        if len(self.sequence) < 1:
            return None
        else:
            return sum(self.sequence) / len(self.sequence)    
 
    def median(self):
        if len(self.sequence) < 1:
            return None
        else:
            self.sequence.sort()
            return self.sequence[len(self.sequence) // 2]
 
    def stdev(self):
        if len(self.sequence) < 1:
            return None
        else:
            avg = self.avg()
            sdsq = sum([(i - avg) ** 2 for i in self.sequence])
            stdev = (sdsq / (len(self.sequence) - 1)) ** .5
            return stdev
 
    def percentile(self, percentile):
        if len(self.sequence) < 1:
            value = None
        elif (percentile >= 100):
            sys.stderr.write('ERROR: percentile must be < 100.  you supplied: %s\n'% percentile)
            value = None
        else:
            element_idx = int(len(self.sequence) * (percentile / 100.0))
            self.sequence.sort()
            value = self.sequence[element_idx]
        return value
 
# Sample script using this class:
# -------------------------------------------
#    #!/usr/bin/env python
#    import corestats
#
#    sequence = [1, 2.5, 7, 13.4, 8.0]
#    stats = corestats.Stats(sequence)
#    print stats.avg()
#    print stats.percentile(90)
# -------------------------------------------