R help - Aug 2005 - diagonal matrices

Hello all,
 
I have matrices V.i  of dimension n.i x n.i, where i = 1, ..., J, and the  sum
of n.i  equals N.  (and n.i ! = n.j)
 
goal: create one large matrix V, where V has matrices V.i on diagonal.
 
I create each matrix V.i in a for loop (1 to J), so each time I'd like to
augment V with the
most recently calculated V.i, such that I'll have V after the final
iteration of the for loop.
 
question: how to initialize V and do the augmentation.   any advice much
appreciated.
 
cheers,
dave 
 
ps - please respond directly to afshar@miami.edu, thanks!
 
 

	[[alternative HTML version deleted]]

Have a look at adiag in the magic package.

On 8/20/05, Afshartous, David <afshart at exchange.sba.miami.edu>
wrote:
> 
> Hello all,
> 
> I have matrices V.i  of dimension n.i x n.i, where i = 1, ..., J, and the 
sum of n.i  equals N.  (and n.i ! = n.j)
> 
> goal: create one large matrix V, where V has matrices V.i on diagonal.
> 
> I create each matrix V.i in a for loop (1 to J), so each time I'd like
to augment V with the
> most recently calculated V.i, such that I'll have V after the final
iteration of the for loop.
> 
> question: how to initialize V and do the augmentation.   any advice much
appreciated.
> 
> cheers,
> dave
> 
> ps - please respond directly to afshar at miami.edu, thanks!
> 
> 
> 
>        [[alternative HTML version deleted]]
> 
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>

On Sat, 20 Aug 2005, Afshartous, David wrote:
> I have matrices V.i of dimension n.i x n.i, where i = 1, ..., J, and the 
> sum of n.i equals N.  (and n.i ! = n.j)
>
> goal: create one large matrix V, where V has matrices V.i on diagonal.
>
> I create each matrix V.i in a for loop (1 to J), so each time I'd like 
> to augment V with the most recently calculated V.i, such that I'll have
> V after the final iteration of the for loop.
>
> question: how to initialize V and do the augmentation.  any advice much 
> appreciated.
It is probably best to pre-create a matrix and fill in the blocks.  As in

V <- matrix(0, N, N)
# let n be a vector of what you called n.i
n0 <- c(0, cumsum(n))
for(i in 1:J) {
    ind <- (n0[i]+1):n0[i+1]
    V[ind, ind] <- V.i
}
>
> cheers,
> dave
>
> ps - please respond directly to afshar at miami.edu, thanks!
Please set that as your reply address to ease the lot of your helpers.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595