Multiplying Elements of arrays: Inner product

*To*: mathgroup at smc.vnet.net*Subject*: [mg68497] Multiplying Elements of arrays: Inner product*From*: Gopinath Venkatesan <gopinathv at ou.edu>*Date*: Tue, 8 Aug 2006 06:28:31 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

I have to dot multiply cd (3x3 matrix) by ab (3x1 column vector). Also I defined values for the first row and the diagonal elements of cd matrix, as well as defined the column vector ab with values. Now ab = {1, 2, 3}, and cd = {{1, 2, 3}, {b[2,1], 1, b[2,3]}, {b[3,1], b[3,2], 1}}. I expect the ef to be {14, 2+b[2,1]+3b[2,3], 3+b[3,1]+2b[3,2]} column vector. But it returns the first element in unevaluated form as 1.1+2.2+3.3. Why is this so? How to make it evaluate them? Thanks for the suggestions. Please see below for my example. ab = Array[a, 3]; cd = Array[b, {3, 3}]; ef = Array[c, 3]; Do[cd[[i, i]] = 1, {i, 1, 3}]; cd[[1, 2]] = 2; cd[[1, 3]] = 3; Do[ab[[i]] = i, {i, 1, 3}]; Do[ef[[i]] = 0, {i, 1, 3}]; Do[ef[[i]] = ef[[i]] + cd[[i, k]].ab[[k]], {i, 1, 3}, {k, 1, 3}]; Gopinath

**Follow-Ups**:**Re: Multiplying Elements of arrays: Inner product***From:*Sseziwa Mukasa <mukasa@jeol.com>