[Maxima-discuss] Fwd: matrix problem

[Jan B. <bro...@gm...>]

Hi,  below I tried to define a memoising matrix function but without success. However I found an elegant solution see below

(%i1) f[x]:=(X[1,1]:cos(x),X[2,1]:cos(x)*2,X[3,1]:sin(x),genmatrix(X,3,1));
(%o1) f  := (X     : cos(x), X     : cos(x) 2, X     : sin(x), 
       x      1, 1            2, 1              3, 1
                                                            genmatrix(X, 3, 1))
(%i2) numer:true;
(%o2)                                true
(%i3) Y:expand(f[3]+matrix([2],[1],[4]));
                           [  1.010007503399555   ]
                           [                      ]
(%o3)                      [ - 0.9799849932008908 ]
                           [                      ]
                           [  4.141120008059867   ]


My question is: can I do the same thing but without using the  expand  function (e.g. are there some variables that I can set to true that work)?


Begin forwarded message:

> From: Jan Brosius <bro...@gm...>
> Subject: matrix problem
> Date: 8 Jul 2014 18:17:00 GMT+2
> To: "max...@li..." <max...@li...>
> 
> Hi,
> 
> I can define 
> 
> genmatrix(A[phi],3,1}
> 
> but how do I assign a value to e.g. A[phi][2,1]. See below the maxima output
> 
> (%i1) genmatrix(A[phi],3,1);
>                                 [ A   (1, 1) ]
>                                 [  phi       ]
>                                 [            ]
> (%o1)                           [ A   (2, 1) ]
>                                 [  phi       ]
>                                 [            ]
>                                 [ A   (3, 1) ]
>                                 [  phi       ]
> (%i2) A[phi][2,1]:=cos(phi);
> 
> define: argument cannot be an atom or a subscripted memoizing function; found: 
>                                                                      (A   )
>                                                                        phi
>                                                                            2, 1
>  -- an error. To debug this try: debugmode(true);
> 
> (%i3) A[phi][2,1]:cos(phi);         
> 
> assignment: cannot assign to (A   )
>                                phi
>                                    2, 1
>  -- an error. To debug this try: debugmode(true);
> 
> thx for any help
> Jan