#!/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]
        self.use_fastselect = False  # switch the algorithm used for percentiles
    
    
    def print_sequence(self):
        # print the sequence (newline delimited)
        for item in self.sequence:
            print item
    
    
    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:
            seq.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 or 1)) ** .5
            return stdev
    
    
    def percentile(self, percentile):
        if self.use_fastselect:
            # get fastselect here: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/466330
            import fastselect
            
        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))
            if self.use_fastselect:            
                # fastselect algorithm.  see fastselect for performance details
                value = fastselect.select(element_idx, self.sequence)
            else:
                self.sequence.sort()
                value = self.sequence[element_idx]
        return value