[SciPy-user] skew and kurtosis return different types
Jarrod Millman
millman at berkeley.edu
Wed Oct 10 14:20:33 EDT 2007
Hey John,
I agree moments of a distribution should be of type float. Currently,
it is for everything except skew and Pearson's kurtosis:
>>> scipy.stats.moment(a)
0.0
>>> scipy.stats.variation(a)
0.58315293025701254
>>> scipy.stats.skew(a)
array(0.0)
>>> scipy.stats.kurtosis(a)
-1.2002400240024003
>>> scipy.stats.kurtosis(a,fisher=False)
array(1.7997599759975997)
We could fix this by either having the functions subtract zero or make
a method call:
>>> scipy.stats.skew(a)
array(0.0)
>>> scipy.stats.skew(a) - 0
0.0
>>> scipy.stats.skew(a).tolist()
0.0
>>> scipy.stats.skew(a).item()
0.0
Does it make any difference if we do it one way or another? Are there
any situations where returning an array with 1 element is importantly
different than returning a float? If we want all the moments to
return values of the same type, my preference would be to use the
.item method.
--
Jarrod Millman
Computational Infrastructure for Research Labs
10 Giannini Hall, UC Berkeley
phone: 510.643.4014
http://cirl.berkeley.edu/
More information about the SciPy-User
mailing list