Re: matrix times a vector

*To*: mathgroup at smc.vnet.net*Subject*: [mg49024] Re: [mg49002] matrix times a vector*From*: Sseziwa Mukasa <mukasa at jeol.com>*Date*: Tue, 29 Jun 2004 04:49:52 -0400 (EDT)*References*: <200406280813.EAA04270@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

On Jun 28, 2004, at 4:13 AM, David Salomon wrote: > Question: > > The input {{a,b}, {c,d}}.{x,y} generates the output {a x+b y,c > x+d y}. > > How can I get the output x{a,b}+y{c,d} ? > > This is a special case of lists with two elements. How > can I extend this computation in an elegant way to lists > with N elements? > Plus @@ MapThread[Times, {{{a, b}, {c, d}}, {x, y}}] But because Mathematica treats {a,b} and {c,d} as vectors {a x+c y,b x+d y} is the result which is equivalent to your desired output assuming {a,b} and {c,d} can be treated as vectors. Replacing {{a,b},{c,d}} and {x,y} in the above expression by your desired N element lists will work assuming the N element sublists can be treated as vectors. Regards, Ssezi

**References**:**matrix times a vector***From:*David Salomon <david.salomon@csun.edu>