From: Martin Maechler <maechler_at_stat.math.ethz.ch>

Date: Wed 14 Dec 2005 - 20:35:34 EST

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Dec 14 20:48:13 2005

Date: Wed 14 Dec 2005 - 20:35:34 EST

>>>>> "HenrikB" == Henrik Bengtsson <hb@maths.lth.se>

>>>>> on Wed, 14 Dec 2005 17:05:32 +1100 writes:

HenrikB> Hi,

HenrikB> help on 'mahalanobis' (in the stats package in Rv2.2.0) now says:

HenrikB> "Description:

HenrikB> Returns the Mahalanobis distance of all rows in 'x' and the vector HenrikB> mu='center' with respect to Sigma='cov'. This is (for vector 'x') HenrikB> defined as

HenrikB> D^2 = (x - mu)' Sigma^{-1} (x - mu)"

HenrikB> It does return D^2 as written. However, would the HenrikB> text be more clear if it says "Returns the HenrikB> _squared_ Mahalanobis distance D^2..." instead? If HenrikB> so, then text in the example code, e.g. "##- Here, HenrikB> D^2 = usual Euclidean distances" and the title of HenrikB> the first plot will also have to be updated.

Indeed, thank you!

Committed {even to R-beta}.

HenrikB> Compare this with what dist() in the same package HenrikB> returns. When asking for the Equlidean distance HenrikB> (matrix) between rows in a matrix, we get D not HenrikB> D^2, e.g. dist(c(1,3)) == 2. ______________________________________________R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Dec 14 20:48:13 2005

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