On Sun, May 23, 2010 at 10:18 PM, TianWei <[email protected]> wrote:
> In the file sage/stats/basic_stats.py, we have the following code for
> the std() function (calculates standard deviation):
>
> 200 if bias:
> 201 # population standard deviation
> 202 if isinstance(x, (int,long)):
> 203 return sqrt(x/ZZ(len(v)))
> 204 return sqrt(x/len(v))
> 205 else:
> 206 # sample standard deviation
> 207 if isinstance(x, (int,long)):
> 208 return sqrt(x/ZZ(len(v)))
> 209 return sqrt(x/(len(v)-1))
>
> In line 208, when the "bias" argument is False, the denominator is
> len(v) instead of len(v) - 1. The docstring says it should be dividing
> by len(v) - 1.
>
> Is this a bug?
Yes, definitely. I've cc'd Andrew Hou, who wrote this code -- maybe
he'll post a quick fix.
Even better -- you could fix the bug and contribute to Sage:
http://sagemath.org/doc/developer/
If anybody creates a ticket about this, be sure to respond to this
email with a link to the ticket (on trac:
http://trac.sagemath.org/sage_trac/).
-- William
>
> -- Tianwei
>
> --
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--
William Stein
Professor of Mathematics
University of Washington
http://wstein.org
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