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

 From "Nick Cox" To Subject st: RE: Re: RE: summing up matrix elements Date Tue, 8 Nov 2005 17:59:30 -0000

```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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```