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RE: st: RE: matrix creation


From   "Maarten Buis" <[email protected]>
To   <[email protected]>
Subject   RE: st: RE: matrix creation
Date   Fri, 2 Dec 2005 17:26:34 +0100

Here is an example that works in Stata 8.2

*---------------example--------------
sysuse auto, clear
reg price mpg rep78 headroom
matrix A = e(V)

matrix B = A /*just to make a matrix with the same dimensions*/

forvalues i = 1/4 {
	forvalues j = 1/4{
		matrix B[`i',`j'] = A[`i',`i'] + A[`j',`j'] - 2 * A[`i',`j']	
	}
}	
*----------end example---------------

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology 
Vrije Universiteit Amsterdam 
Boelelaan 1081 
1081 HV Amsterdam 
The Netherlands

visiting adress:
Buitenveldertselaan 3 (Metropolitan), room Z214 

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------

-----Original Message-----
From: [email protected] [mailto:[email protected]]On Behalf Of U.A.QU.AP
Sent: vrijdag 2 december 2005 18:26
To: [email protected]
Subject: Re: st: RE: matrix creation

Thanks to N. Cox, but in my original message I mean
I'd like to create a matrix B such that
B[i,j]=A[i,i]+A[j,j]-2*A[i,j]
I'm a user of Stata 8.2



---- Original message ----
>Date: Fri, 2 Dec 2005 14:07:09 -0000
>From: "Nick Cox" <[email protected]> 
>Subject: st: RE: matrix creation 
>To: <[email protected]>
>
>I am not sure if you mean what you say, as
>B appears on both sides here. However,
>assuming by Statalist convention that
>you are using Stata 9.1, in Mata the
>following code, given a matrix A, may help:
>
>B = A
>
>for(i = 1; i <= rows(A) ; i++) {
>       for(j = 1; j <= cols(A); j++) {
>               B[i,j] = A[i,i] + A[j,j] - 2 * A[i,j]
>       }
>}
>
>Note how close is it to your algebra.
>
>Nick
>[email protected]
>
>U.A.QU.AP (a.k.a. AbdelRahmen)
>
>> I have a square matrix A (100x100). I'd to create a matrix
B
>> such that
>> B[i,j]=A[i,i]+B[j,j]-2*A[i,j]
>
>*
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>*   http://www.ats.ucla.edu/stat/stata/

*
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*
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