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Re: operation x=x(:)

From: A. Scottedward Hodel
Subject: Re: operation x=x(:)
Date: Wed, 05 May 1999 14:59:07 -0500

>I am testing the ability of octave to replace MatLab in my company. One of the
>biggest drawbacks to use it is the missing ¥x=x(:)¥ operation. For all not
>knowing what it does: it will convert any colum or row vector into a colum
>vector. Many of our MatLab scripts and toolboxes rely on this to convert any
>vector into a defined state. I can¥t realy imagine it is not implemented sofar.
>but where do I have to hit octave to do it?

    An equivalent function (for vectors x) in octave is
    x = vec(x)

    octave:1> vec([1 2])
    ans =


    octave:2> vec([1;2])
    ans =


    although this will fail to warn you if the initial value of x was not
    a vector (row or column).

    octave:3> vec([1 2; 3 4])
    ans =


    The behavior you've described would require editing the octave C++ source;
    John Eaton could address the "where" much better than I could.  I think that
    this sort of topic was addressed in the help list a year or so ago, but
    I don't recall the conclusion that was drawn.

>Another topic - if anyone of the maintainers is listening:
>Taken the case I think octave is able to replace MatLab I would like to port
>a good part of MatLab¥s signal toolbox with the help of an internship. I would
>be very happy if one of the ocatve team could tell me how this can be done
>without violating the legal rights of MathWorks. Of course we would follow the
>little pledge from octave¥s signal toolbox help and share the results ;)

    Regarding "porting" a toolbox: to avoid ethical and copyright problems, 
    it is important that one rather "develops" a toolbox without reference to 
    the matlab  toolboxes.  It *is* a lot of work.  However, the end result may 
    be more pleasing, since in the development of a new toolbox you can try to 
    correct the annoyances you've had to deal with in the Matlab toolbox 
    they might be).  

    Do take a look at the controls toolbox; there may be some items there that
    you'd like to take advantage of in such a rewrite (data structure, frequency
    response, block diagram manipulations, analog<->digital, etc.)

A S Hodel Assoc. Prof. Dept Elect Eng, Auburn Univ,AL  36849-5201
On leave at NASA Marshall Space Flight Center (256) 544-1426
Address until 15 Mar 2000:Mail Code ED-13, MSFC, Alabama, 35812

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