Re: Don't want to calculate scalar product

*To*: mathgroup at smc.vnet.net*Subject*: [mg19743] Re: Don't want to calculate scalar product*From*: Martin Kraus <Martin.Kraus at informatik.uni-stuttgart.de>*Date*: Wed, 15 Sep 1999 03:52:59 -0400*Organization*: Institut fuer Informatik, Universitaet Stuttgart*References*: <7ree45$489@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Toshiyuki (Toshi) Meshii wrote: > > Hi, > > I understand that one of the unique point of Mathematica is that you don't > have to be conscious about whether a vector is a "row" or a "column" vector. Actually I always think of Mathematica lists as row vectors. (Though some functions treat them as if they were column vectors. :) > However, I think there is a case in which you have to specify whether you > want Mathematica to recognize a vector as a row vector or a column vector. > Let me explain my case. > > a={1,2,3}; b={4,5,6} > > I want to define "a" as a column vector (3x1 matrix) and "b" as a row vector > (1x3 matrix). Well, just do it: a={{1},{2},{3}}; b={{4,5,6}}; a.b returns {{4, 5, 6}, {8, 10, 12}, {12, 15, 18}} > I expect the product > a.b > as a 3x3 matrix, but the answer Mathematica gives is a scalar product "32". product. The inner product is what "." calculates. For the outer product use Outer[Times, a, b] with the vectors a and b: a = {1, 2, 3}; b = {4, 5, 6}; Outer[Times, a, b] {{4, 5, 6}, {8, 10, 12}, {12, 15, 18}} > Please give me an advice to get the 3x3 matrix as a product. > > -Toshi Hope that helps Martin Kraus