Rkadapt Bug - SMath

#1 Pubblicato: 03/10/2016 02:42:28

Jean Giraud

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Page9 Scrap RK.sm (41,24 KiB) scaricato 1876 volta(e).

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Radovan Omorjan 03/10/2016 04:28:00

#2 Pubblicato: 03/10/2016 04:32:44

Radovan Omorjan

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Hmm...Interesting example, but it does not work for me in Mcad 15 either?

Regards,
Radovan

[attach]

When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!"

#3 Pubblicato: 03/10/2016 04:57:56

Вячеслав Мезенцев

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I don't know how to convert implicit form into explicit. If you show me the rules for the numeric case I'll add such feature.

Russia ☭ forever, Viacheslav N. Mezentsev

#4 Pubblicato: 03/10/2016 14:31:25

Jean Giraud

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Viacheslav, Radovan: as simple as that
add a dummy 0 to the vector of RK solution
to meet the length of the IC !!!

#5 Pubblicato: 03/10/2016 16:00:44

Radovan Omorjan

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Wrote
Viacheslav, Radovan: as simple as that
add a dummy 0 to the vector of RK solution
to meet the length of the IC !!!

Ah yes, but this is the standard "trick" in Mathcad when you want to give some parameter to the ODE. The derivative of that parameter is zero - like your dummy second value.
Here, if I understood this well, you might use SMath in a better way - giving parameters as third, fourth,...argument (not possible in Mathcad).
Your example might be this way as well

When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!"

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Вячеслав Мезенцев 04/10/2016 02:12:00

#6 Pubblicato: 04/10/2016 05:45:23

Вячеслав Мезенцев

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Functions from ODE Solvers plugin use the rules from Mathcad help. If you have two initial conditions this means that you have the second order ODE and f(t,y) must be a vector with two rows.

Citazione
Arguments:

init is either a vector of n real initial values, where n is the number of unknowns, or a single scalar initial value, in the case of a single ODE.

Rewriting a Higher-Order ODE as a System of First-Order ODEs.pdf (142,98 KiB) scaricato 1329 volta(e).

Russia ☭ forever, Viacheslav N. Mezentsev

#7 Pubblicato: 04/10/2016 11:13:35

Jean Giraud

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Thanks Viacheslav,

Very useful for those not familiar [never had Mathcad].
I have added the automatic RK vector extractor D(x,Y).

Jean

ODE Euler_rkf4 EDU.sm (31,04 KiB) scaricato 1563 volta(e).

#8 Pubblicato: 04/10/2016 22:21:15

Jean Giraud

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...just change variables for new names.
or copy/paste the section in blank sheet.
Smath is very reactive wrt variables.

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