[Octave-bug-tracker] [bug #56393] missing deval function for ode

[Carlo de Falco]

Follow-up Comment #5, bug #56393 (project octave):

Re: comment #3 

The latest version of matlab I have access to is 2018b and the code I posted
works there. 

Anyway that behaviour is still documented in the current web documentation for
the latest Matlab version so I assume it is still supported.

Re: comment #4

IIRC there was someone looking into how this is handled in Matlab at the time
when we ported ode45 and ode23 from odepkg into Octave. 

AFAIR the basic idea is that


[t,y] = ode45(odefun,t,y0)


and 


sol = ode45(odefun,t,y0)
y = deval(sol,t)


should return exactly the same results. 
for this to work Matlab stores into the "sol" structure
all the information needed to use the same interpolator
as is used during the integration.

In particular for ode45 and ode23 the solution and derivatives
at the intermediate stages of RK5 and RK3 method are stored and
the appropriate Hermite interpolation methods are used.

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