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[no subject]
Tony
Peter A. Lachenbruch
Department of Public Health
Oregon State University
Corvallis, OR 97330
Phone: 541-737-3832
FAX: 541-737-4001
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Tirthankar Chakravarty
Sent: Monday, May 03, 2010 2:09 PM
To: [email protected]
Subject: Re: st: Calculating Mahalanobis distance
<>
To calculate the centred Mahalanobis distance between two variables as
here try this:
***********************************************
clear*
sysuse auto, clear
mata
real vector maha_dist(string scalar varlist, string scalar touse)
{
real matrix mX
real matrix mZ
st_view(mX=., ., tokens(varlist), touse)
mZ = mX :- mean(mX)
return(sqrt(diagonal(mZ*invsym(cross(mZ, mZ)/(rows(mZ)-1) )*mZ')))
}
end
cap prog drop md
program define md
version 11
syntax varlist [if] [in], [GENerate(string )]
marksample touse
mata: vReturn = maha_dist("`varlist'", "`touse'")
getmata `generate' = vReturn
end
md weight length, gen(md_w_l)
su md_w_l
***********************************************
You can put this in two -foreach- loops to calculate the distance
between a bunch of variables.
T
2010/5/3 Schijven, Mario <[email protected]>:
> Hi all,
>
> Does anyone know whether Stata has a pre-programmed command to compute Mahalanobis distance? So far, I've manually computed the Euclidean distance between two sets of firms in a dataset, but I need to compute the Mahalanobis distance. If Stata cannot do this, perhaps someone knows how to do it in Excel (i.e., how do I modify the formula for calculating Euclidean distance into one for Mahalanobis distance)?
>
> All the very best and many thanks in advance,
>
> Mario Schijven
> Mays Business School
> Texas A&M University
>
> *
> * For searches and help try:
> * http://www.stata.com/help.cgi?search
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
--
To every ù-consistent recursive class ê of formulae there correspond
recursive class signs r, such that neither v Gen r nor Neg(v Gen r)
belongs to Flg(ê) (where v is the free variable of r).
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/