[R] odesolve/lsoda differences on Windows and Mac

Thomas Petzoldt petzoldt at rcs.urz.tu-dresden.de
Thu Jul 28 11:05:58 CEST 2005

On 27 Jul 2005, Peter Dalgaard wrote:

> One thought: Integrating across input pulses is a known source of
> "turbulence" in lsoda. You might have better luck integrating over
> intervals in which the input function is continuous.
> Tweaking the lsoda tolerances is another thing to try.

Yes, that's also our experience. Where I am usually succesful
when playing with the tolerances or the interpolation rule of external
pulses, some of our students use the fixed step rk4 algorithm and some
others wrote their own integrators in R.

I have heared that several people had plans to provide alternative ODE
integrators for R but I currently do not know about the state of these
projects. It wold be nice if they might post this to the list in order to
avoid double work.

> I haven't seen lsoda fail like that, but it's not too surprising that
> marginal cases show platform dependency (i.e. the integrator just
> fails on Mac and barely succeeds on PC).

Aha, I see. It should be regarded carefully when publishing examples that
result in "marginal cases" as the common user would expect that R is
platform independent.

Thomas P.

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