[Numeric-python-jp 23] Fwd: [ numpy-Bugs-514588 ] MLab.cov(x,x)!=MLab.cov(x)

[藁谷 克則]

藁谷です。

Numerical Python の開発者の一人から、
上記のバグを修正したというメールを受け取りました。

次のリリースには反映されるということです。
待ちきれない人は、
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/numpy/Numerical/Lib/MLab.py.d 
iff?r1=1.20&r2=1.21
で変更点をご覧ください。


以下メールのやり取りからの抜粋。
>To: noreply ＠ sourceforge.net
>From: noreply ＠ sourceforge.net
>Subject: [ numpy-Bugs-514588 ] MLab.cov(x,x)!=MLab.cov(x)
>Sender: nobody <nobody ＠ sourceforge.net>
>Date: Mon, 25 Feb 2002 11:41:00 -0800
>
>Bugs item #514588, was opened at 2002-02-07 15:38
>You can respond by visiting:
>http://sourceforge.net/tracker/?func=detail&atid=101369&aid=514588&group_id 
>=1369
>
>----------------------------------------------------------------------
>
>Comment By: Travis Oliphant (teoliphant)
>Date: 2002-02-25 11:41
>
>Message:
>Logged In: YES
>user_id=5296
>
>This bug has been fixed in CVS and will appear in the next release. Thank 
>you for reporting it.
>
>
>----------------------------------------------------------------------
>
>Comment By: Nobody/Anonymous (nobody)
>Date: 2002-02-12 22:24
>
>Message:
>Logged In: NO
>
>If you have MATLAB(TM), you can check the result of cov(x,x) in MATLAB.
>I'm sorry to say I don't have MATLAB(TM), all I have is Octave, S, R,
>  and Numerical-Python.
>Octave defines cov(x,y) as follows.
>
>octave:1> help cov
>cov is the function defined from: 
>/usr/local/share/octave/2.0.16/m/statistics/ba
>se/cov.m
>
>  usage:  cov (x [, y])
>
>  The (i,j)-th entry of cov (x, y) is the covariance between the i-th
>  variable in x and the j-th variable in y.
>
>  For matrices, each row is an observation and each column a variable;
>  vectors are always observations and may be row or column vectors.
>
>  cov (x) is cov (x, x).
>
>
>Additional help for builtin functions, operators, and variables
>is available in the on-line version of the manual.  Use the command
>`help -i <topic>' to search the manual index.
>
>Help and information about Octave is also available on the WWW
>at http://www.che.wisc.edu/octave/octave.html and via the
>help-octave ＠ bevo.che.wisc.edu mailing list.
>octave:2>
>
>You can see how Octave language implements cov(x,y) by installing Octave.
>
>R(S langugae clone) also defines cov(x,y).
>
> > x<-seq(1,3)
> > y<-seq(1,3)
> > cov(x)
>[1] 1
> > cov(x,y)
>[1] 1
> >
>
>So, Current implementation for MLab.cov(x,y) differs what Octave and R 
>user expects.
>
>
>----------------------------------------------------------------------

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