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matrix multiplication [message #911]

Mon, 22 March 1993 14:51

c1dje
Messages: 2
Registered: March 1993

Junior Member

I am trying to apply a list of rotation matrices to a matching list
of vectors, i.e. a vector of three-vectors and a vector of 3x3 matrices. I
can correctly apply a rotation matrix between a vector and a matrix, but
now the vector is a list of vectors and the matrix is a list of matrices.
I could handle all of this with a "for" loop, but that is inefficient in
IDL; I would like IDL to loop over all of the indices internally. My
problem is creating the rotation matrix with the proper ordering for matrix
multiply (#).
Previously I multiplied a 3-vector by a 3x3 matrix:

[v1,v2,v3] # [[a1,a2,a3],[a4,a5,a6],[a7,a8,a9]]

but now all of the variables are vectors (of matching length) so V is Nx3
and A is Nx3x3. I can transpose V so that it is 3xN but IDL requires the
argument of transpose to be 1D or 2D, not 3D as the rotation matrix
appears. How do I generate the 3x3xN matrix from nine vectors of length N?
Will this collective matrix multiply even work as I expect?

David
============================================================ ===================
David Edelsohn T.J. Watson Research Center
c1dje@watson.ibm.com P.O. Box 218
+1 914 945 3011 (Tieline 862) Yorktown Heights, NY 10598
"The Church doesn't have problems with sex; the world does" -- Vatican official
"A good theory should fit on a T-shirt" -- Astronomer at Jan 1992 AAS meeting

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[Message index]

		matrix multiplication By: c1dje on Mon, 22 March 1993 14:51
		Re: Matrix multiplication By: Haje Korth on Fri, 14 November 2003 09:48
		Re: matrix multiplication By: Chris[6] on Tue, 28 October 2008 13:59
		Re: matrix multiplication By: russ[1] on Tue, 28 October 2008 14:32
		Re: matrix multiplication By: David Fanning on Tue, 28 October 2008 11:42
		Re: matrix multiplication By: Vince Hradil on Tue, 28 October 2008 19:17

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