Re: A question of matrix multiply, who can solve it?
- To: mathgroup at smc.vnet.net
- Subject: [mg25687] Re: A question of matrix multiply, who can solve it?
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Thu, 19 Oct 2000 04:35:16 -0400 (EDT)
- References: <8sjkht$g2h@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Chen Jisheng: A .B , short for Dot[A,B], is what gives matrix multiplication (more generally tensor multiplication) A B, which you used, give the entry by entry product. -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 "Chen Jisheng" <chenjs at iopp.ccnu.edu.cn> wrote in message news:8sjkht$g2h at smc.vnet.net... > Dear Sir, > > As a beginning user, I find a mistake of Mathematic 4.0(/3.0 for student). > > That is about the multipy method of matrix. > > For example, as I input the two matrices: > > A={a[1, 1], a[1, 2], a[1, 3], a[1, 4], a[1, 5]} > {a[2, 1], a[2, 2], a[2, 3], a[2, 4], a[2, 5]} > {a[3, 1], a[3, 2], a[3, 3], a[3, 4], a[3, 5]} > {a[4, 1], a[4, 2], a[4, 3], a[4, 4], a[4, 5]} > {a[5, 1], a[5, 2], a[5, 3], a[5, 4], a[5, 5]}, > B={{b[1, 1], b[1, 2], b[1, 3], b[1, 4], b[1, 5]}, > > {b[2, 1], b[2, 2], b[2, 3], b[2, 4], b[2, 5]}, > > {b[3, 1], b[3, 2], b[3, 3], b[3, 4], b[3, 5]}, > > {b[4, 1], b[4, 2], b[4, 3], b[4, 4], b[4, 5]}, > > {b[5, 1], b[5, 2], b[5, 3], b[5, 4], b[5, 5]}}, > > then calculate the result of A B. The mathematics gives the following > result: > > A B={{a[1, 1] b[1, 1], a[1, 2] b[1, 2], a[1, 3] b[1, 3], > > a[1, 4] b[1, 4], a[1, 5] b[1, 5]}, > > {a[2, 1] b[2, 1], a[2, 2] b[2, 2], a[2, 3] b[2, 3], > > a[2, 4] b[2, 4], a[2, 5] b[2, 5]}, > > {a[3, 1] b[3, 1], a[3, 2] b[3, 2], a[3, 3] b[3, 3], > > a[3, 4] b[3, 4], a[3, 5] b[3, 5]}, > > {a[4, 1] b[4, 1], a[4, 2] b[4, 2], a[4, 3] b[4, 3], > > a[4, 4] b[4, 4], a[4, 5] b[4, 5]}, > > {a[5, 1] b[5, 1], a[5, 2] b[5, 2], a[5, 3] b[5, 3], > > a[5, 4] b[5, 4], a[5, 5] b[5, 5]}}. > > As all knows, this is not correct. I think it is terrible. > > Do you think so? How can improve it? > > Looking forward to receiving the reply. > > J.-S CHen, > Institute of Particle Physics, > Hua-Zhong Normal University, > Wuhan 430079,China > >