diff options
Diffstat (limited to 'numpy/core/fromnumeric.py')
| -rw-r--r-- | numpy/core/fromnumeric.py | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/numpy/core/fromnumeric.py b/numpy/core/fromnumeric.py index da169d017..471a50a8c 100644 --- a/numpy/core/fromnumeric.py +++ b/numpy/core/fromnumeric.py @@ -1671,9 +1671,11 @@ def std(a, axis=None, dtype=None, out=None, ddof=0): Notes ----- The standard deviation is the square root of the average of the squared - deviations from the mean, i.e. var = sqrt(mean((x - x.mean())**2)). The - computed standard deviation is computed by dividing by the number of - elements, N-ddof. + deviations from the mean, i.e. var = sqrt(mean(abs(x - x.mean())**2)). + The computed standard deviation is computed by dividing by the number of + elements, N-ddof. The option ddof defaults to zero, that is, a + biased estimate. Note that for complex numbers std takes the absolute + value before squaring, so that the result is always real and nonnegative. Examples -------- @@ -1734,9 +1736,10 @@ def var(a, axis=None, dtype=None, out=None, ddof=0): Notes ----- The variance is the average of the squared deviations from the mean, - i.e. var = mean((x - x.mean())**2). The computed variance is biased, + i.e. var = mean(abs(x - x.mean())**2). The computed variance is biased, i.e., the mean is computed by dividing by the number of elements, N, - rather than by N-1. + rather than by N-1. Note that for complex numbers the absolute value is + taken before squaring, so that the result is always real and nonnegative. Examples -------- |