Wrote

I can't solve the system....

Wrote

Just for my curiosity, are you obliged by your codes (and which) to use the parabola-rectangle diagram?

Wrote

Hope this solves your problem: (declare the boundaries). Just for my curiosity, are you obliged by your codes (and which) to use the parabola-rectangle diagram?
Regards,
Alvaro

Wrote

Your system is over-killed from gyzmas [subscripts] and from carrying units at the design stage. You have J, N in the solve bloc. Smath is not a clone of the crappy PTC Mathcad.

Wrote

Thank you Davide, now I have dowloaded/read the NTC2018, it looks like EC2-1.1.

• Maxima couldn't reduce functions to polynomials;
• roots founds 2 equations with 3 variables;
• FindRoots I do not understand.

Wrote

Old school. See AlgLib 3.1x.

Wrote

I purged units in function definitions: Forum example w-o units.sm (54 КиБ) скачан 45 раз(а).

Now I have three different errors:

• Maxima couldn't reduce functions to polynomials;
• roots founds 2 equations with 3 variables;
• FindRoots I do not understand.

I think now I'm closer to the solution. Any other suggest?

PS: sometimes I used a while loop to solve single equations, but I've some desing difficulties with 2 variables...

Wrote

...

I think maxima Solve() can't handle functions containing conditional statements. Using boolean expressions won't help, as these aren't translated to maxima.

Wrote

Wrote

...

I think maxima Solve() can't handle functions containing conditional statements. Using boolean expressions won't help, as these aren't translated to maxima.

Hi Martint. I guess that what you have in Maxima for handle conditionals is unit_step(x) = ( 0 if x <= 0 and 1 for x > 0 ).

Or can use U(x) = (1 + signum(x))/2 which takes U(0)=1/2.

I don't try to use it, but guess that both can be used for Solve, Integrate and Diff inside SMath calling Maxima.

Best regards.
Alvaro.

Wrote

Wrote

Old school. See AlgLib 3.1x.

Many thanks Viacheslav, your NL solver found the solution in few seconds! Forum example w-o units_2.sm (48 КиБ) скачан 41 раз(а).

Now I'll test it in a more complex engineering problem

Wrote

Wrote

Here a test with 3 equations: someting went wrong, because the solution is expected to be near the origin and function value in the origin is very large... I can't find a graphical solution in this case...

Your project is not visible:
1. NO units whatsoever, nowhere.
2. Visible values
3. NO subscript
As it looks, you seem seeking for the intersection of 2 double integral.
You may proceed like in real Engineering project, i.e:
1. Tabulate each double integral in matrix.
2. Unwrap each matrix in single vector, adjoin fake index.
3. Plot 2D to see intersection.
4. Interpolate, solve for more exact graphical solution.

Wrote

... subjective of visibility.

Integrate Compendium_17 DOUBLE Fourier CoC.sm (55 КиБ) скачан 39 раз(а).

• I'd improve the solution speed;
• I still can't evaluate the Jacobian matrix.

Wrote

I purged units in function definitions:

#20 Опубликовано: 27.05.2020 17:35:19

SteelCat

3 сообщений из 47 понравились пользователям.

Группа: User

Wrote

good news , the AlgLib solver works, but:

• I'd improve the solution speed;
• I still can't evaluate the Jacobian matrix.

I think the use of Jacobian would improve the efficiency (https://www.mathworks.com/help/optim/ug/nonlinear-least-squares-with-full-jacobian.html)
Also the use of some eval()...
Forum example w-o units_4-BIS.sm (83 КиБ) скачан 39 раз(а).

Any suggestions?

Forum example w-o units_4-BIS.sm (80 КиБ) скачан 44 раз(а).

It seems that the issue was due to the Jacob() function: I defined manually the Jacobian matrix, but Smath still do not show me the result...

Physics is like sex. Sure, it may give some practical results, but that’s not why we do it. (R. Feynman)