compute-mean-and-variance.py

#!/usr/bin/env python3

import sys
import math
from collections import Counter

counts = Counter()

for line in sys.stdin:
    vals = line.strip().split()[1:]
    vals = [int(x) for x in vals]
    n_vals = len(vals)

    mean = sum(vals) / n_vals
    squared_errors = [(x - mean)*(x-mean) for x in vals]
    unbiased_variance = sum(squared_errors) / (n_vals-1)

    counts["%.0f\t%.0f" % (sum(vals), unbiased_variance)] += 1

for record, count in counts.items():
    print("%s\t%s" % (count, record))