
Re: Working with arrays
Posted:
Jun 17, 2013 6:17 AM


Use a period instead of a CenterDot, as you did in the "Second case".
Cheers, Kevin
On 6/16/2013 5:12 AM, amannucci wrote: > I thought I understood variables. This sequence completely mystifies me: > Clear[lA, xtest] > lA = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}; > xtest = {4, 5, 6}; > lA\[CenterDot]xtest (* First case *) > {{a, b}, {c, d}} . {x, y} (* Second case *) > > The output is: > > {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}\[CenterDot]{4, 5, 6} > > {a x + b y, c x + d y} > > How do I force matrix multiplication to actually occur, as in the second answer? Why does Mathematica do the matrix multiply in the second case but not the first? > > Thanks for any help. > > Tony >

