Page9 Scrap RK.sm (41 KiB) downloaded 60 time(s).

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

Regards,
Radovan
[attach]

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.

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

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

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.

Quote

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 KiB) downloaded 63 time(s).

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 KiB) downloaded 51 time(s).

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