Thomas Richard

Mr. Thomas Richard

2623 Reputation

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12 years, 156 days
Maplesoft Europe GmbH
Technical professional in industry or government
Aachen, North Rhine-Westphalia, Germany

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These are answers submitted by Thomas Richard

0.*I and -0.*I are not simplified automatically because these outputs (typically of a numerical function evaluation) may contain information on branching behaviour of that function - this is hinted at under the ?fnormal description.

That worksheet is quite old, apparently it was created in the 1990s. In the meantime, some new commands have been added, e.g. plots:-plotcompare which is very helpful for visualizing basic properties of functions in the complex domain.

Some eyecatchers can be made with Fractals:-EscapeTime package. Engineers benefit from various commands in DiscreteTransforms and SignalProcessing, e.g.

Are you interested in plotting specifically, or in complex numbers generally?

First, you will need to insert a multiplication symbol between q and I in the assignment to eq1. Note that qI would be an unknown variable.

Next, apply evalc as follows:

a := evalc(Re(eq1));
b := evalc(Im(eq1));

I tend to say yes, the equation can be solved analytically - but I don't know any direct method, sorry.

What you can try in Maple is to apply the identify command to the numerical solution, at increasing values of Digits:

A := Matrix(2, 2, [[2, 1], [1, -1]]):
B := Vector[column](2, [3, 1]):
Q := Matrix(2, 2, [[3, 0], [0, 2]]):
R := Matrix(1, 1, [[3]]): 
with(LinearAlgebra):
Digits := 72:
nsol := CARE(A,B,Q,R);
idsol := identify(nsol);
exsol := allvalues(idsol);

For Digits>=54, identify is successful with one element of the solution matrix; and Digits=72 seems to be the lowest setting to obtain all of them.

I have not tried with L and condition number (see CARE option 'output'), though.

Maple is using log4j version 1.2.3; see e.g. the note under ?copyright (Apache log4j is listed in section Open Source).

Affected versions range from 2.0 to 2.14.1.

These attributes are not configurable. The code editor is really meant to be tiny. If you think it's useful to have additional configuration settings, please submit an SCR via the More menu of MaplePrimes. Thank you.

Hardware specs of your laptop should still be sufficient for Maple 2021. I suppose by "latest stable Ubuntu" you mean one of the supported versions; please see our System Requirements.

To determine whether it's really a memory issue, I would suggest running a thorough test such as MemTest86.

Good luck!

See the Contact link at the top of the page. There is no separate e-mail address.

Your expectation is not unreasonable; in fact, pdsolve is trying a factorization (albeit unsuccessfully), as can be seen from the diagnostic output. Other methods (separation ansatz) are successful, but return a very long solution which can be simplified somewhat:

restart:
eq1:=E*D(II)(x)*D[1](psi)(x,t)+E*II(x)*(D[1]@@2)(psi)(x,t)-G*A(x)*psi(x,t)+G*A(x)*D[1](v)(x,t):
eq1:=convert(eq1,diff);
eq2:=-(G*D[1](A)(x)*psi(x,t)+G*A(x)*D[1](psi)(x,t))+(G*D[1](A)(x)*v(x,t))+G*A(x)*(D[1]@@2)(v)(x,t)-m(x)/G*D[2](v)(x,t):
eq2:=convert(eq2,diff);
sys:=[eq1,eq2]:
infolevel[pdsolve]:=5:
sol:=pdsolve(sys,[psi(x,t),v(x,t)]);
length~(sol);
ot:=odetest(sol,sys);
ssol:=simplify~(sol): length~(ssol);

I've let this run over the lunch break, and saw the results afterwards.

Probably you have already found our FAQ page which confirms your observation. No need to delete any files if you are unsure, but modifying their date should be harmless. Please try that first.

This problem only affects time-limited licenses. The expiry date can be found in your license.dat file.

By the way, it's good that you made the SN field (activation code) unreadable before uploading the screenshot!

ExpandSteps is designed for products (or fractions) of polynomials - please see its help page. It gets confused by the presence of trig expressions. The error message could be better, but even then it won't solve the problem.

What you can do is: replace sin(theta) by s and cos(theta) by c, then ExpandSteps will succeed quickly - but also produce a lot of output! Backsubstitution will make it even (a bit) worse.

The activation code (aka Purchase Code) needs to be entered into the activation tool, which is typically launched at the end of the installation process for most of our products. If you get stuck, please send an e-mail with that code and error message (or other symptoms, if any) to custservice@maplesoft.com. See https://www.maplesoft.com/support/ for more options.

Do not post your code on MaplePrimes nor on any other public web sites.

This is a very common problem, and the background of the error message is explained on the help page that opens when entering

?cannotdetermineifthisexpression

(Clicking on the error message does not bring you there, unfortunately.)

The best solution for your code example is #2, i.e. to use the operator form when plotting:

plot(funktion, r1 .. r2);

This will ensure that evaluation of x is deferred so that the conditional statement (if...then...end if) inside the function definition can be executed.

Notice that both the argument to funktion and the left hand side of the equation that specifies the range have been omitted. So you even save a few keystrokes. :-)

The output of a Maple command can be suppressed by terminating it with a colon. Didn't that work for what you tried?

What did you enter in Maple?

Perhaps post one or two examples of your PDEs. You may also include a download link to your text file.

Please send your Maple worksheet (mw file) to support@maplesoft.com, or upload it via https://www.maplesoft.com/contact/webforms/support.aspx. You may also attach your PDF file, but the worksheet is needed to reproduce the problem.

Since you are evaluating Maple, I suppose you have the current version 2021.1 - otherwise please specify. Your platform (OS version) may also be relevant.

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