MaplePrimes - answers and comments on Question, Vector Calculus Multiply Error

Jacobian

Alec Mihailovs — Sat, 11 Jun 2011 10:25:58 Z

Jacobian produces a Matrix, and you need a Vector, which can be obtained from it as

Dwx := Jacobian(x(p,w),[w])[..,1];

diff and D[2] should work assuming that you executed with(VectorCalculus) somewhere earlier, if you specify the (Maple's) dot product explicitely,

Dwx.x(p,w)^%T;

Alec

Thanks for your response. I'm looking to

AlwaysLearning — Sat, 11 Jun 2011 23:04:57 Z

Thanks for your response. I'm looking to apply the outer product on the two vectors. I've played with it a little bit more and here's a better example:

f := a^2 * <x*y,x+y>;

df := diff(f,a); # --> column vector

df f^+; # --> outer product gives 2x2 matrix

diff(f,a) f^+; # --> Error, (in rtable/Product) invalid arguments

'diff(f,a)' f^+; # --> delaying evaluation pretty prints expression with no derivates taken

%; # --> evaluates expression above and displays same outer product 2x2 matrix

Looks like I need to delay evaluation so the outer product function can properly 'see' that diff(f,a) is a column vector.

I'm knew to this stuff, if somebody knows a good tutorial about how Maple evaluates expressions, that'll help.

dot

Alec Mihailovs — Sun, 12 Jun 2011 00:57:21 Z

@AlwaysLearning

As I said, you shouldn't make the multiplication implicit (using a space). It's much better to use a dot instead - then Maple won't interpret it as * which produces those errors.

In general, the best tutorials available are Maple manuals (available from the Help menu and for download from the Documentation Center.) Or posts on this site. Everything else (books etc.) is outdated.

Alec

Got it, thanks! Didn't think that . works

AlwaysLearning — Sun, 12 Jun 2011 18:30:09 Z

Got it, thanks! Didn't think that . works for outer product as well.