I have nothing against row and column matrixes - just the sloppiness of calling them vectors.
On 10/8/07, John Randall <[EMAIL PROTECTED]> wrote: > > Devon McCormick wrote: > > I find the APL/J general use of "arrays" and what they are to be simple, > > useful, and consistent. > > I agree with Ralph that calling a 1xN matrix a row vector and an Nx1 > > matrix > > a column vector is, > > at least, sloppy language. > > I am not convinced. If you don't have row and column matrices > (a) matrix multiplication is not associative > (b) the results have the wrong shape > > mp=:+/ .* > > a=:1 2 > b=:3 4 > c=:5 6 > > vc=:2 1 $ c > vb=:1 2 $ b > va=:2 1 $ a > > a mp (b mp c) > 117 > (a mp b) mp c > 121 > a mp b > 11 > va mp vb > 3 4 > 6 8 > > Best wishes, > > John > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > -- Devon McCormick, CFA ^me^ at acm. org is my preferred e-mail ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
