Re: Matrix Multiplication (with a twist)

*To*: mathgroup at smc.vnet.net*Subject*: [mg69013] Re: Matrix Multiplication (with a twist)*From*: "sashap" <pavlyk at gmail.com>*Date*: Sat, 26 Aug 2006 04:40:03 -0400 (EDT)*References*: <ecmhcp$9kl$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Bruce Colletti wrote: > For matrix A = {{e,f},{g,h}} and B = {{a,b},{c,d}}, Mathematica returns their product > > A.B = {{ae+cf,be+df},{ag+ch,bg+dh}} > > However, I want to treat multiplication of numeric variables as noncommutative in order to instead obtain the result > > {{ea+fc, eb+fd},{ga+hc,gb+hd}} > > How would this be done in v5.2? Thanks. > > Bruce Hi Bruce, try Inner: In[1]:= mA = {{e, f}, {g, h}}; mB = {{a, b}, {c, d}}; In[3]:= Inner[NonCommutativeMultiply, mA, mB] Out[3]= {{e**a + f**c, e**b + f**d}, {g**a + h**c, g**b + h**d}} Oleksandr Pavlyk Wolfram Research