RE: Re: Matrix Expansion question to Mathgroup
- To: mathgroup at smc.vnet.net
- Subject: [mg47869] RE: [mg47842] Re: Matrix Expansion question to Mathgroup
- From: "David Park" <djmp at earthlink.net>
- Date: Thu, 29 Apr 2004 03:05:38 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Harold, I'm not certain that simply appending rows or appending columns would be a legitimate operation in tensor calculus. In any case, the Tensorial package at my web site has commands that handle these kind of operations. It allows the CircleTimes notation with slot arguments for tensors and there is a ConstructDirectProduct command. Next there are SetTensorValues and SetTensorValueRules commands. These have an option that allows the user to not only set single values for components, but to also set array values to components. For example, basis vectors may be given a list of xyz components for values. The Help documentation also has a notebook on "Matrices, Arrays and Tensors". It illustrates the relation between tensor index notation and working directly with matrices and arrays. The direct product of two tensors is obtained by using Outer. The more interesting constructions are forming contractions on arbitrary slots. Tensorial has a command ContractArray that will do tensorial contraction on a Mathematica style array. (Hartmut Wolf helped me with the routine.) David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: Harold Noffke [mailto:Harold.Noffke at wpafb.af.mil] To: mathgroup at smc.vnet.net Larry: Your question is not trivial, because what you have is a rank-3 tensor, and I was not able to get AppendRows and AppendColumns to work for rank-3 tensors A and B in a simple programming example. It is obvious that each of your matrix elements are lists, and the only lists you want affected by AppendRows and AppendColumns are the outermost two -- i.e., in dimensions 1 and 2. MathGroup ... Do we have packages available which extend AppendRows and AppendColumns to tensors? Regards, Harold