From help-octave-request at bevo dot che dot wisc dot edu Wed Feb  5 10:43:23 2003
Subject: Re: late Re: A Simple Matrix Construction Question
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: David Bateman<David dot Bateman at motorola dot com>
Cc: <alrl1 at alu dot um dot es>, <help-octave@bevo.che.wisc.edu>
Date: Wed, 5 Feb 2003 10:42:24 -0600

On  5-Feb-2003, David Bateman <David dot Bateman at motorola dot com> wrote:

| If this is what you want to do, why not do for example
| 
| m = 4;
| n = 5;
| y = rand(1,n);
| x = y(ones(m,1),:);
| 
| where x will now be a m by n matrix with m copies of y,
| one per row. Indexing should definitively be more
| computationally efficient than doing a matrix multiply
| which is O(n^3).

Indexing is not necessarily more efficient.  See

  http://www.octave.org/mailing-lists/help-octave/2003/133

jwe



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