From maintainers-request at octave dot org Wed Feb  9 11:25:39 2005
Subject: Re: Moving code from octave-forge to octave [Was: polyderiv problem?]
From: Michael Creel <michael dot creel at uab dot es>
To: maintainers at octave dot org
Cc: Paul Kienzle <pkienzle at users dot sourceforge dot net>,         Joe Koski <jkoski11@comcast.net>
Date: Wed, 09 Feb 2005 17:56:11 +0100


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On Wednesday 09 February 2005 16:50, David Bateman wrote:
> I looked at the patches directory of octave-forge and it seems that all
> of the patches here, except one are either already included in the main
> part of octave or superseded by other changes to octave. The only
> remaining patch to consider is M-v-ops-2.1.31.patch that allows the
> extension of ./, .*, etc to allow Matrix by vector arguments. Its not
> clear how this ports to NDArrays, since in fact the NDArray
> generalization means that singleton dimensions in one of the args should
> force the matrix to be duplicated allow that dimension of the other arg.
>
> Do we want to do that? In any case, matlab doesn't support this
> behavior, and it might hid some dimensioning errors from the since
> something like "randn(N,1)+randn(1,N)" would create an N-by-N matrix...
> It is clear however, that the existing patch is of no use as a basis for
> this as it is against an octave version prior to the introduction of
> NDArrays. So all of the patches in octave-forge might be dumped...
>
> Regards
> David

I sent this message to David, but I meant to send it to all, so here it is:

This is a behavior that I have found very useful in languages like Gauss and 
Ox. Maybe it would be possible to allow it only for matrices and vectors, but 
not NDArrays? Or maybe a function would do the job. I attach a quck hack for 
consideration. Michael
m_x_v.m

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function result = m_x_v(m,v)
	if !ismatrix(m)
		error("m_x_v: first arg must be a matrix");
	endif
	if !isvector(v)
		error("m_x_v: second arg must be a vector");
	endif

	[rm, cm] = size(m);
	[rv, cv] = size(v);
	
	if (rm == rv)
		v = kron(v, ones(1,cm));
		result = m .* v;
	elseif (cm == cv)
		v = kron(v, ones(rm, 1));	
		result = m .* v;
	else
		error("m_x_v: dimension of vector must match one of the dimensions of the matr
ix");	
	endif
endfunction




 

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