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st: Re: RE: Re: RE: summing up matrix elements


From   "R.E. De Hoyos" <redeho@hotmail.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Re: RE: Re: RE: summing up matrix elements
Date   Tue, 8 Nov 2005 18:15:03 -0000

Offhand, I can't think of any reason why anyone
with Stata 9 would prefer that. Nor, I imagine,
would Jeroen if he were to be asked.
I have access to Stata 9 only when I am in the University, in my laptop I have version 8.

Rafa

----- Original Message ----- From: "Nick Cox" <n.j.cox@durham.ac.uk>
To: <statalist@hsphsun2.harvard.edu>
Sent: Tuesday, November 08, 2005 5:59 PM
Subject: st: RE: Re: RE: summing up matrix elements



You may be thinking of Jeroen Weesie's -matsum-.
Offhand, I can't think of any reason why anyone
with Stata 9 would prefer that. Nor, I imagine,
would Jeroen if he were to be asked.

STB-39 dm49 . . . . . . . . . . . . . . . . . . . . Some new matrix commands
(help matfunc, varfunc if installed) . . . . . . . . . . . J. Weesie
9/97 pp.17--20; STB Reprints Vol 7, pp.43--48
collection of new matrix commands; several for explicit matrices
and a few for implicit matrices (i.e., variables)

Nick
n.j.cox@durham.ac.uk

R.E. De Hoyos


Both your solutions work fine, thanks a lot.
I though there was a non-mata matrix function similar to
mata's -sum(C)-
Nick Cox

. mata : sum_r = (sum(C) - trace(C)) / 2

R.E. De Hoyos

>> > Is there a way to to get a scalar containing the sum of the
>> > off-diagonal
>> > elements of a pre-defined matrix?
>> >
>> > For instance, define matrix C  as a correlation matrix. I
>> > want to know what
>> > is the sum of correlations between the various elements in C.
>> > Therefore I
>> > need the sum of all elements in C minus the sum of the
>> > diagonal elements
>> > (-trace(C)-) and finally divide it by 2 (I am assuming
matric C is
>> > symetric).
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