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RE: st: RE: Adding Matrices generated from a loop


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: Adding Matrices generated from a loop
Date   Fri, 24 Aug 2007 16:50:36 +0100

Perhaps I should add that initialising the sum matrix
to be zeros can be best. Initialising the sum matrix
to be the first matrix is not, of course, the only
way to do it. 

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

Nick Cox
 
> Well, initialise outside the loop, and add each replaced 
> t_i to the sum so far each time round the loop. Naturally, 
> all the matrices must be conformable. 
> 
> Nick 
> n.j.cox@durham.ac.uk 
> 
> Nadeem Shafique
>  
> > Sorry for not providing complete information, I am trying it using
> > Mata. Following is the code i am trying to execute.
> > 
> > **************************************************************
> > ******************************
> >   for (i=1; i<=rows(info); i++)
> > 					{
> >                                                             
>      v_i =
> > panelsubmatrix(v, i, info)
> > 				m_i = panelsubmatrix(m,i,info)
> > 				n_i = panelsubmatrix(s,i,info)
> > 				n = mean(n_i)
> > 				t_i=v_i*m_i*n
> > 
> >                     }
> > 
> > ****************** I want to sum all these t_i in one matrix say "t"
> 
>  
> > On 8/24/07, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> > > There may be subtleties here I am missing, but
> > > I would initialise
> > >
> > >        sum <- first_matrix
> > >
> > > and then loop over the other matrices
> > >
> > >        sum <- sum + next_matrix
> > >
> > > This is pseudocode.
> > >
> > > Otherwise I can't tell what's troubling you about
> > > this. As the details will depend on whether
> > > you are using Stata or Mata, your naming structure,
> > > what else you are doing with these matrices,
> > > whether the number is predictable in advance, etc.,
> > > none of which is indicated, I'll leave it there.
> 
> > > Nadeem Shafique
> > >
> > > > I want to add several matrices (say K) of the same order, 
> > suppose the
> > > > matrices to be added are comming from a loop, how can i 
> > calculate the
> > > > following
> > > >
> > > >                 K
> > > >                 Sum    X_i
> > > >                 i=1
> > > > where X_i is the ith Matix

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