Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2006
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2006

[Date Index] [Thread Index] [Author Index]

Search the Archive

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


  • Prev by Date: Re: Two strange problems with a notebook...
  • Next by Date: Re: Using Map with function that has options...
  • Previous by thread: Re: Newbie question about column sums of arrays
  • Next by thread: Re: Multiplying Elements of arrays: Inner product