6.0.28 + matrix exponential - some issues

pviton's picture

Please see attached sci file. (Note that the issue about exp not being grayed out may be related to one mentioned by jm as Bug2 in his Initial Impressions post for 6.0.28).

matrix_expl.sci138.1 KB
pviton's picture

Quick update on Maple vs

Quick update on Maple vs MuPad in computing a matrix exponential: Maple agrees with the MuPad response that jm posted, but also gives an answer for the case q[1,2]+q[1,3]=q[2,3].

pviton's picture

In response to jm: getting an

In response to jm: getting an answer
by adding a carriage return is interesting -
I hadn't thought of that. Is there a reason why
this would be expected to work? It looks as
though the response agrees with Maple,
but I'll need to check at home.
I'll post further only if it doesn't agree.

I continued to play around with this
and the following appears to work:

1. Define the matrix to be, say A.
2. Write down exp(A) in math and
evaluate it.

The result looks correct, and is actually
noticeably faster than Maple.

Also, by chance I noticed that if in the
original posting I put the cursor
in the "exp" and then do Evaluate, this
also works. (As it does with the
cursor somewhere in the matrix itself).

So it appears that the problem may be
with trying to select and then
Evaluate. Is this a general rule ---
that selecting and evaluating is
unreliable? If so, it ought to
be stressed.

jm's picture

1. The issue about exp not

1. The issue about exp not being grayed out certainly seems related to the one I mentioned as Bug2 in my Initial Impressions post for 6.0.28.

2. The issue of parentheses getting re-sized when something is inserted or changed is one I have come across a lot with SWP 6.0.27. Sometimes, matched parentheses become unmatched on screen and for editing. Sometimes, as in your case, the PDF shows them as small, sometimes as large. I haven't managed to work out what causes any of these to occur. But it is clearly something that needs investigating for the next release.

3. I added to your .sci file by first entering exp (in math mode), then entering paired parentheses and copied in your matrix. The parentheses did not resize. Compute > Evaluate was grayed out until I added a carriage return. Once I had done that, it gave the result in the attached file. Is this the same answer that Maple gives?