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Re: Ignorance


From: Robert T. Short
Subject: Re: Ignorance
Date: Tue, 06 Mar 2012 09:46:26 -0800
User-agent: Mozilla/5.0 (X11; Linux i686; rv:10.0.2) Gecko/20120216 Thunderbird/10.0.2

On 03/05/2012 07:34 PM, John W. Eaton wrote:
On  5-Mar-2012, Robert T. Short wrote:

| I don't know the dimensions or the direction a-priori.  The obvious
| answer is 1:N followed by a repmat but there are so many cute little
| octave tricks that I was hoping there was something really clever.

Given

   x = 1:4;
   y = ones (3, 1);
   z = ones (3, 4);

here are the ways I can think of:

   Repmat:

     repmat (x, [3,1])

   Kron:

     kron (x, y)

   Indexing:

     x(y,:)

   Outer product:

     y * x

   Broadcasting:

     z .* x

Are there any others?

jwe


Excellent. The kind of thing I was looking for was the indexing solution. Using kron, outer product, sums, broadcasting involve computation so I would rather not use them for something like this. Thanks for the tips.

Bob


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