Re: matrices & polynomials in mathematica

*To*: mathgroup at smc.vnet.net*Subject*: [mg27270] Re: matrices & polynomials in mathematica*From*: "Allan Hayes" <hay at haystack.demon.co.uk>*Date*: Sun, 18 Feb 2001 02:52:07 -0500 (EST)*References*: <96iqj6$d90@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

PolyMatrixReplace[poly_, var_, matr_] := With[{Id = IdentityMatrix[Length[matr]]}, Fold[#1.matr + #2 Id &, 0 matr, #] &[Reverse[CoefficientList[poly, var]] ] ] Example: poly= 3 +x +x^3; mat = {{1,2},{2,5}}; PolyMatrixReplace[poly, x, mat] {{33,72},{72,177}} -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 "news.tue.nl" <student at tue.nl> wrote in message news:96iqj6$d90 at smc.vnet.net... > Hi, > > I have the following problem. > I have written a mathematica-module that automatically produces a certain > polynomial as a result. But I want another module to use this first module > and fill in a matrix in this polynomial. > for example: f[x]=1+x+x^2 > But when I compute f[A] where A is a matrix, mathematica interprets 1 as a > matrix filled with ones in stead of the identity-matrix. And A^2 is > pointswise multiplication in stead of matrix-multiplication. > Is there an option to let Mathematica know that the polynomial works on > matrices? > > Chris > > PS. I am aware of the possibility to multiply matrices using . (dot) but the > problem is that the polynomial is the result of some computations and I need > to have mathematica interpret this polynomial on matrices automatically. > > > >