RE: Lack of matrix slicing documentation

[Ciotti, Louis A]

This functionality is documented in Chapter 10 section 1

<quote>

10.1 Index Expressions 

An index expression allows you to reference or extract selected elements
of a matrix or vector. 

Indices may be scalars, vectors, ranges, or the special operator `:',
which may be used to select entire rows or columns. 

<end quote>

-----Original Message-----
From: address@hidden [mailto:address@hidden 
Sent: Thursday, September 23, 2004 7:12 AM
To: address@hidden
Subject: Lack of matrix slicing documentation

The documentation very much need an easy accessible explanation of how
to work on parts of matrixes.


Here is my short story of how I almost did not start to use Octave,
and why.

I chose Octave because I thought it would have easy ways of accessing
parts of matrixes. Found nothing in the documentation, and did the
project with C instead.

New project, with need of eigenvectors. Did most of it in C, exported
matrices to Octave, and used a lot of "for" loops to move elements.

Then avoided Octave for a long time. Forgot the lack of sub-matrix
operators, returned to Octave, and again found nothing about it in the
documentation, and did it in C again.

Took a peek at Matlab, and found that it could do sub-matrix operations,
like:
  A(1:N-1,:) = A(2:N,:);
Tried that on Octave as an experiment, and it worked!

Had I seen that in the manual, I would have used Octave from the
start, and I guess this apply to other people than me as well.

So, to make Octave more popular and more widely used, I suggest
putting this in the manual, in the Matrix intruduction section.

Kim0,  M.Sc. Physics.



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-------------------------------------------------------------
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
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