def cov(xs, ys):
"""共分散"""
n = len(xs)
avg_x = mean.mean(xs)
avg_y = mean.mean(ys)
xs = map(lambda x: x - avg_x, xs)
ys = map(lambda x: x - avg_y, ys)
return sum(x * y for x, y in zip(xs, ys)) / n
def ssd(xs):
"""偏差平方和
sum of squared deviation
"""
avg = mean.mean(xs)
return sum(map(lambda x: (x - avg) ** 2, xs))
def test_mean(xs, expected):
assert mean.mean(xs) == expected
assert mean.mean(xs) == stats.mean(xs)