Re: Dot Product of Vectors

*To*: mathgroup at smc.vnet.net*Subject*: [mg89069] Re: Dot Product of Vectors*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Sun, 25 May 2008 03:20:10 -0400 (EDT)

On 5/24/08 at 3:55 AM, gregory.lypny at videotron.ca (Gregory Lypny) wrote: >I've got two n x k matrices called X and Y. I'd like to compute an >n x 1 vector whose elements are the dot products of corresponding >rows of X and Y, that is, >{{X[[1]].Y[[1]]}, {X[[2]].Y[[2]]}, {X[[3]].Y[[3]]}, ... >{X[[n]].Y[[n]]}. >I found that this can be done using MapThread as >MapThread[Dot, { X, Y}], >which is straightforward. I'm curious, given that there a zillion >ways to do any given calculation in Mathematica, if anyone knows of >another way that is as compact. Another simple way to get the same result would be: Total@Transpose[x y]