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Meaning of outer product [message #31428]

Fri, 12 July 2002 17:33

Paul Sorenson
Messages: 48
Registered: May 2002

Member

Greetings,

IDL documentation says: "Note - If A and B arguments are vectors, then C =
MATRIX_MULTIPLY(A, B) is a matrix with C_ij = A_iB_j. Mathematically, this
is equivalent to the outer product. . . ." But I'm having difficulty
reconciling this with my understanding of outer product. . .

c.x = a.y*b.z - a.z*b.y
c.y = a.z*b.x - a.x*b.z
c.z = a.x*b.y - a.y*b.x

... which yields a vector (c) instead of a 2D array. Can anyone shed some
light on this?

-Paul Sorenson

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Re: Meaning of outer product [message #31528 is a reply to message #31428]

Fri, 19 July 2002 13:57

jeyadev
Messages: 78
Registered: February 1995

Member

In article <3d37695a_2@corp-goliath.newsgroups.com>,
Paul Sorenson <aardvark62@msn.com> wrote:
> Thanks, James and M. Katz. Your responses really helped clear up this issue
> for me. To summarize: the IDL documentation is correct in referring to C_ij
> = A_iB_j as the outer product. Other resources that refer to the cross
> product as the "outer product" are using the term more loosely.
^^^^^^^

Incorrectly, would be better :-)

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Surendar Jeyadev jeyadev@wrc.xerox.bounceback.com

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