From e00524b473cf1efe3454643176200f34733f0d3c Mon Sep 17 00:00:00 2001 From: Kevin Sheppard Date: Fri, 6 Feb 2015 16:25:58 -0500 Subject: [PATCH] DOC: Clarify definition of kurtosis used Added explation that kurtosis returned is Fisher's kurtosis, also known as excess kurtosis. Also cleans up the kurtosis function to remove some unused computations. --- pandas/core/generic.py | 4 +++- pandas/core/nanops.py | 1 - 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/pandas/core/generic.py b/pandas/core/generic.py index b2adfae744db7..f454af5df9c90 100644 --- a/pandas/core/generic.py +++ b/pandas/core/generic.py @@ -3998,7 +3998,9 @@ def stat_func(self, axis=None, skipna=None, level=None, nanops.nanskew) cls.kurt = _make_stat_function( 'kurt', - 'Return unbiased kurtosis over requested axis\nNormalized by N-1', + 'Return unbiased kurtosis over requested axis using Fisher''s ' + 'definition of\nkurtosis (kurtosis of normal == 0.0). Normalized ' + 'by N-1\n', nanops.nankurt) cls.kurtosis = cls.kurt cls.prod = _make_stat_function( diff --git a/pandas/core/nanops.py b/pandas/core/nanops.py index b3d8f2b67ffab..9587d0d4a9043 100644 --- a/pandas/core/nanops.py +++ b/pandas/core/nanops.py @@ -511,7 +511,6 @@ def nankurt(values, axis=None, skipna=True): D = (values ** 4).sum(axis) / count - A ** 4 - 6 * B * A * A - 4 * C * A B = _zero_out_fperr(B) - C = _zero_out_fperr(C) D = _zero_out_fperr(D) if not isinstance(B, np.ndarray):