"""This file contains code for use with "Think Stats",
by Allen B. Downey, available from greenteapress.com

Copyright 2010 Allen B. Downey
License: GNU GPLv3 http://www.gnu.org/licenses/gpl.html
"""

def PercentileRank(scores, your_score):
    """Computes the percentile rank relative to a sample of scores."""
    count = 0
    for score in scores:
        if score <= your_score:
            count += 1

    percentile_rank = 100.0 * count / len(scores)
    return percentile_rank

scores = [55, 66, 77, 88, 99]
your_score = 88

print 'score, percentile rank'
for score in scores:
    print score, PercentileRank(scores, score)
print

def Percentile(scores, percentile_rank):
    """Computes the value that corresponds to a given percentile rank. """
    scores.sort()
    for score in scores:
        if PercentileRank(scores, score) >= percentile_rank:
            return score

def Percentile2(scores, percentile_rank):
    """Computes the value that corresponds to a given percentile rank.

    Slightly more efficient.
    """
    scores.sort()
    index = percentile_rank * (len(scores)-1) / 100
    return scores[index]

print 'prank, score, score'
for percentile_rank in [0, 20, 25, 40, 50, 60, 75, 80, 100]:
    print percentile_rank, 
    print Percentile(scores, percentile_rank),
    print Percentile2(scores, percentile_rank)