[Numpy-discussion] Standard Deviation (std): Suggested change for "ddof" default value

Eelco Hoogendoorn hoogendoorn.eelco at gmail.com
Tue Apr 1 16:06:02 EDT 2014


I agree; breaking code over this would be ridiculous. Also, I prefer the
zero default, despite the mean/std combo probably being more common.


On Tue, Apr 1, 2014 at 10:02 PM, Sturla Molden <sturla.molden at gmail.com>wrote:

> Haslwanter Thomas <Thomas.Haslwanter at fh-linz.at> wrote:
>
> > Personally I cannot think of many applications where it would be desired
> > to calculate the standard deviation with ddof=0. In addition, I feel that
> > there should be consistency between standard modules such as numpy,
> scipy, and pandas.
>
> ddof=0 is the maxiumum likelihood estimate. It is also needed in Bayesian
> estimation.
>
> If you are not eatimating from a sample, but rather calculating for the
> whole population, you always want ddof=0.
>
> What does Matlab do by default? (Yes, it is a retorical question.)
>
>
> > I am wondering if there is a good reason to stick to "ddof=0" as the
> > default for "std", or if others would agree with my suggestion to change
> > the default to "ddof=1"?
>
> It is a bad idea to suddenly break everyone's code.
>
>
> Sturla
>
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