Re: row vectors changed to column vectors?

[Christoph Dalitz]

On Tue, 10 Feb 2004 17:46:55 +0100
"Christian T. Steigies" <address@hidden> wrote:
>
> > >BTW, if you are creating vectors by doing things like
> > >
> > >  clear a;
> > >  for i = 1:N
> > >    a(i) = something();
> > >  end
> > >
> > >then you should probably rethink your method, because this type of
> > >loop the vector A to be resized N times, which will be slow.
> 
> Yes, it is slow, what do you suggest? Should I create a matrix with
> zero(N,1) first? Looks as if it is just a few ms difference.
> 
If your matrix entries can be computed in some way, might look for a way
to create your matrix with builtin vector/matrix operations, eg. 
[1^2,2^2,3^2,...,n^2]
could be created with (1:n).^2.

You can find more suggestions in
http://lionel.kr.hs-niederrhein.de/~dalitz/data/lehre/CBM/vektorisierung-4up.ps.gz
(it is in German, but the formula are understandable supralingual)

Hope this helps,

Christoph



-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
-------------------------------------------------------------