Re: [Outer [Times, , ] ] Question

*To*: mathgroup at smc.vnet.net*Subject*: [mg45824] Re: [Outer [Times, , ] ] Question*From*: Bill Rowe <readnewsciv at earthlink.net>*Date*: Mon, 26 Jan 2004 01:53:33 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

On 1/25/04 at 3:04 AM, MichaelSMcCain at cs.com wrote: > I want to take a Column Vector and multiply it by a Row Vector to create an > "Outer" Matrix. > In other words, I want to take a 5x1 Column Vector and multiply it by a 1x4 > Row Vector and output a 5x4 Matrix. > I then want to add several of these Matrices together and obtain a "final" > Matrix. > I tried the following: > x1 = {1, -1, -1, 1, 1}; > y1 = {1, 1, -1, -1}; <snip> > m1 = MatrixForm[Outer [Times, x1, y1] ] The problem is your usage of MatrixForm here. MatrixForm adds a wrapper to the matrix. But that means Mathematica no longer sees m1 as a matrix. That is MatrixQ[m1] False if you get rid of the MatrixForm all will work as you want. If you want to display the matrix as a traditional matrix you can either set the default format type as Traditional Form or do the following MatrixForm[m1=Outer[Times, x1, y1]] As an aside you don't need Outer to perform this task. All you need is Transpose at {x1}.{y1} That is define the two things to be multiplied as matrices and use the built in matrix multiplication operator ".". -- To reply via email subtract one hundred and four