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From: "Milos Milenkovic" <m.milenkovic@mathworks.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: Special matrix multiplication
Date: Sat, 4 Feb 2012 14:40:33 +0000 (UTC)
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"John D'Errico" <woodchips@rochester.rr.com> wrote in message <jgj876\$2rh\$1@newscl01ah.mathworks.com>...
> "Milos Milenkovic" <m.milenkovic@mathworks.com> wrote in message <jgj6ir\$rj7\$1@newscl01ah.mathworks.com>...
> > Dear,
> > suppose that we have two matrices, where each element has three values like follows:
> >
> > A=[(a1,b1,c1), (a2,b2,c2); (a3,b3,c3), (a4,b4,c4)]
> > B=[(d1,e1,f1), (d2,e2,f2); (d3,e3,f3), (d4,e4,f4)]
> >
> > Now, I have to multiply these two matrices, and that is matrix C=A*B
> >
> > C=[ c11=(a1,b1,c1)*(d1,e1,f1)+(a2,b2,c2)*(d3,e3,f3), c12=(a1,b1,c1)*(d2,e2,f2)+(a2,b2,c2)*(d4,e4,f4); c21=(a3,b3,c3)*(d1,e1,f1)+(a4,b4,c4)*(d3,e3,f3), c22=(a3,b3,c3)*(d2,e2,f2)+(a4,b4,c4)*(d4,e4,f4)]
> >
> > where the most important here is the low for multiplying these three-value numbers is:
> >
> > (ai,bi,ci)*(di,ei,fi) = (bi*di+ei*(ai-bi), bi*ei , ei*ci+bi(fi-ei))
> >
> > Please, how to do this, I have a dozen of this matrices with 700x700 in dimension approximately.
> > Best,
> > Milos
>
> While there is no magic that will let you do this for
> no effort on your part, I still don't see the problem.
>
> You can just write a function that takes a pair of triads,
> and "multiplies" them by your rule.
>
> Then just write another function that takes a pair of
> matrices, and multiplies them, again as per your rule.
>
> Its just a few loops. Whats the problem? You can even
> build a special class for the purpose, where you define
> a "multiply" to be anything you wish between class
> members.
>
> Its not even a big problem, but even if it was, you
> eat even an elephantine computational problem one
> byte at a time. Just start writing.
>
> John

Dear John,
please be a little more explicit, I know all of that, but I do not have a time to start from zero.
I suppose that I can use some standard matrix multiplication function written in Matlab and make certain changes.
Best,
Milos
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