Re: Maple 8 | subs and matrices

cooch17_at_NOSPAMverizon.net
Date: 11/05/04 

Date: Fri, 05 Nov 2004 11:54:03 -0500

On Fri, 05 Nov 2004 15:55:17 GMT, Joe Riel <joer@k-online.com> wrote:

>The linalg package is deprecated; you really should switch to the
>LinearAlgebra package.

OK - sounds like sage advice to start.

>
>> What I want to be able to do is substitute in values for the variables
>> a -> d, using the subs command. But, I don't seem to be able to figure
>> out how one does this.
>>
>> If I try
>>
>> mat:=array([[a,b],[c,d]]);
>> subs(a=0.5,b=0.2,c=1,d=0,mat);
>
>Here are two ways to accomplish this
>
>map2(subs,{a=0.5,b=0.2,c=1,d=0},mat);
>subs(a=0.5,b=0.2,c=1,d=0, eval(mat));
>
>> But, if I use
>>
>> mat:=Matrix([[a,b],[c,d]]);
>> subs(a=0.5,b=0.2,c=1,d=0,mat);
>>
>>
>> Things work fine. OK - there is a difference between array and Matrix.
>> Fine - IF I explicitly define a matrix using Matrix. But, what if I
>> don't, or can't? For example, suppose I derive a Jacobian matrix,
>> using (say)
>>
>> jac:=jacobian(a,[n[1],n[2]]);
>
>Try VectorCalculus:-Jacobian to work with Matrices. Okay, you're now
>wondering (or should be 8-), "how am I supposed to figure that out?"
>Well, I didn't know where it was, either. In fact, one of the reasons
>I continued to use linalg for a while was precisely this; I needed to
>compute jacobians and couldn't find an equivalent in the LinearAlgebra
>package. The solution, at least in the Classic GUI, is to use the
>Full Text Search in the Help menu. Or ask in appropriate forum;
>comp.soft-sys.math.maple is better than sci.math.symbolic because
>it is specific to maple.

Thanks - I ended up discovering the VectorCalculus option just about
the same time you posted your reply.

And, as for the appropriate forum - good point. At one point, there
wasn't a Maple-specific list (or, if there was, my Unviersity news
server didn't have it available).

But, on the larger topic - I wonder if there is a 'rationale' reason
for Maple not being consistent throughout - I don't see an obvious
reason for subs to work for some things, but not others.

Relevant Pages

  • Re: symbolic computation
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  • Re: symbolic computation
    ... Nasser Abbasi wrote: ... linalg is old maple linear algebra package any way, ... Try to enter the above using LinearAlgebra package. ... Mathematica), I did the above in Mathematica 6 and got the answer ...
    (comp.soft-sys.matlab)