[R] cluster with mahalanobis distance

[Ravi Varadhan]

"The manhattan distance and the Mahalanobis distances are quite different. "

This ought to be a candidate for "fortunes".

The way distances are perceived in New York city is very different from that in Calcutta (which is where Professor Prasant Chandra Mahalanobis lived)!  

Ravi.


____________________________________________________________________

Ravi Varadhan, Ph.D.
Assistant Professor,
Division of Geriatric Medicine and Gerontology
School of Medicine
Johns Hopkins University

Ph. (410) 502-2619
email: rvaradhan at jhmi.edu


----- Original Message -----
From: Phil Spector <spector at stat.berkeley.edu>
Date: Wednesday, March 3, 2010 4:24 pm
Subject: Re: [R] cluster with mahalanobis distance
To: Tal Galili <tal.galili at gmail.com>
Cc: r-help at r-project.org, naama <nwolf at technion.ac.il>


> The manhattan distance and the Mahalanobis distances are 
>  quite different.  One of the main differences is that 
>  a covariance matrix is necessary to calculate the Mahalanobis
>  distance, so it's not easily accomodated by dist.  There 
>  is a function in base R which does calculate the Mahalanobis
>  distance -- mahalanobis().  So if you pass a distance matrix
>  calculated by mahalanobis() to the clustering function, you'll
>  get what you want.
>                                   	- Phil Spector
>                                            Statistical Computing Facility
>                                            Department of Statistics
>                                            UC Berkeley
>                                            spector at stat.berkeley.edu
>  
>  
>  On Wed, 3 Mar 2010, Tal Galili wrote:
>  
>  > when you create the distance function to put into the hclust, use:
>  >
>  > dist(x, method = "manhattan")
>  >
>  >
>  > Tal
>  >
>  >
>  >
>  > ----------------Contact
>  > Details:-------------------------------------------------------
>  > Contact me: Tal.Galili at gmail.com |  972-52-7275845
>  > Read me: www.talgalili.com (Hebrew) | www.biostatistics.co.il 
> (Hebrew) |
>  > www.r-statistics.com (English)
>  > ----------------------------------------------------------------------------------------------
>  >
>  >
>  >
>  >
>  > On Wed, Mar 3, 2010 at 9:14 PM, naama <nwolf at technion.ac.il> wrote:
>  >
>  >>
>  >> How can I perform cluster analysis using the mahalanobis distance 
> instead
>  >> of
>  >> the euclidean distance?
>  >> thank you
>  >> Naama Wolf
>  >>
>  >> --
>  >> View this message in context:
>  >> 
>  >> Sent from the R help mailing list archive at Nabble.com.
>  >>
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>  > R-help at r-project.org mailing list
>  > 
>  > PLEASE do read the posting guide 
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>  >
>  
>  ______________________________________________
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>  
>  PLEASE do read the posting guide 
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