Re: Stop mathematica reordering expression during matrix multiply

*To*: mathgroup at smc.vnet.net*Subject*: [mg109408] Re: Stop mathematica reordering expression during matrix multiply*From*: Simon <simonjtyler at gmail.com>*Date*: Sun, 25 Apr 2010 06:26:18 -0400 (EDT)*References*: <hqu8cj$rq1$1@smc.vnet.net>

Hi Robert, I think that what you want to do can be found on the research page of George Stacey Staples: http://www.siue.edu/~sstaple/index_files/research.htm Simon On Apr 24, 3:59 pm, Robert Wright <mathematicaus... at yahoo.com> wrote: > I am using a Graph Theory algorithm which requires that I multiply an edg= e-weighted adjacency matrix with symbolic parts. In my problem, the order o= f the symbols corresponds to the edges that make up a path - for example, x= 2 x1 x7 would indicate that the path progresses from x2 to x1 then x7. The = snag comes when Mathematica reorders the symbols in each expression appeari= ng in the matrix result from multiplying Ci x Cj - is there a way of stoppi= ng this from happening? > > Here is some code that illustrates the problem: > > C1 = {{0, x1, 0, 0}, {x2, 0, x3, 0}, {x4, 0, 0, x5}, {x6, 0, x7, 0}}; > C2 = C1.C1; > MatrixForm@C2 > > The MatrixForm output shows how Mathematica has sequenced the symbols in = 'ascending' order. In my case, I want to preserve the order of the symbols = in the calculated expression: so, for example, row 4 of C1 times column 2 o= f C1 should give x4 x1 and not x1 x4. How do I stop Mathematicafrom reorder= ing the resulting expression?