From octave-sources-request at bevo dot che dot wisc dot edu  Thu Jan 11 01:37:36 2001
Subject: Re: improved/corrected dot.m
From: Dirk Laurie <dirk at calvyn dot puk dot ac dot za>
To: Rolf Fabian <fabian at tu-cottbus dot de>
Cc: "'octave-sources UWISC'" <octave-sources at bevo dot che dot wisc dot edu>
Date: Thu, 11 Jan 2001 09:37:23 +0200

Rolf Fabian skryf:
> Appended is an improved/corrected version of
> the dot script function, which allows for switching between
> the two legal flavours of an inner product definition.
> They differ by returning complex conjugated results
> for input of complex vectors.
> 
>From the mathematical point of view, the dot product of two
column vectors A and B can only be A'*B.  This is because the
relationship  dot(A,A) == norm(A)^2  needs to be satisfied.
It is not a Matlab peculiarity to define it that way, rather
Matlab defines it thus because the inventor of Matlab is a
mathematician.  IMHO it is misleading and dangerous to have
a routine dot.m that could possibly give A.'*B instead.  
I would strongly prefer a separate routine with a different
name for the latter case, e.g. udot.m for "unconjugated dot".

Dirk



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