Derivative of a matrix representation of a quadratic form

*To*: mathgroup at smc.vnet.net*Subject*: [mg5439] Derivative of a matrix representation of a quadratic form*From*: "Nathan C." <nathanc at cs.msu.su>*Date*: Sat, 7 Dec 1996 00:26:14 -0500*Organization*: Comp.Center (RUS), U of Stuttgart, FRG*Sender*: owner-wri-mathgroup at wolfram.com

Is there any function X (perhaps in a Mathematica add-on) that would do the following: X[Dot[Dot[A,x],x],x] ---> Dot[A+Transpose[A],x] X[Dot[Dot[A,x],a],x] ---> Dot[Transpose[A],a] It seems to me that as such this is impossible, as vectors and matrices are all the same to Dot. A realization of X would require something more than Dot, perhaps several functions for various combinations of matrices and vectors. Has anybody already done this? Or does anybody know of a different package that would help in manipulating long matrix expressions? Please reply by email, Thank you! Nathan Cheng