How to get a matrix multiply that considers dimensions?
- To: mathgroup at yoda.physics.unc.edu
- Subject: How to get a matrix multiply that considers dimensions?
- From: pwm at macaw.jhuapl.edu (Phil W. Miller x8335 1-e138)
- Date: Wed, 7 Oct 92 18:54:16 EDT
I just ran into a problem where Mma lack of dimension on a vector caused problems. I need to take the matrix product of a matrix with a vector times its transpose; i.e., (A x) (A x)' I needed the following Mma syntax to get this Outer[Times, A . x, A . x], which is ugly but okay. But if Ax is a matrix instead of a column vector, one needs (A.x) . Transpose[A.x] Is there a general way to do matrix multiplication in Mma where dimension is considered? I thought about it briefly, but do not know how to cope with the fact that one dimensional lists are neither row or column vectors. Your help is appreciated. Phil Miller