Thanks Riccardo for the quick reply and your suggestion.
I'm specifically want to use ARMA, because I use it in my thesis and
benchmark it against a bunch of other interpolators I've implemented.
Once I get that working I'll definitely look into your Kalman-filter
suggestion.
Do you maybe know how to add the time-lags to the DATASET? The gretl API
documentation (and the examples in the source code) are not very
informative on this matter. And how do I set t1 and t2 of the DATSET so
that the ARMA model and get_forecast knows where the samples start and
end (since there are now 2 places where the data starts and ends, not
just 1 as with the usual DATASET used to do a simple forecast).
Regards
Chris
On 2014/05/15 08:02 AM, Riccardo (Jack) Lucchetti wrote:
On Thu, 15 May 2014, GOO Creations wrote:
> Hi,
>
> I'm not sure if this is possible in gretl. I want to interpolate a gap
> of samples with ARMA by using the value to the left and right of the
> gap. If I have data like this:
>
> Time lag: 1 2 3 4 5 6 7 8 9 10 11
> Values: 0 0.1 0.2 0.3 * * * 0.3 0.2
> 0.1 0
>
> The values marked with a star are the gap I want to interpolate (at lag
> 5, 6 and 7: the values should be something like 0.4, 0.5, 0.4 after
> interpolation). How would you go about creating a gretl DATASET with
> these values? And will the get_forecast function work on "predicting"
> the interpolated samples?
> I've always used ARMA for out-of-sample forecasts, but never for
> interpolation, so I'm not sure if this is possible.
This is absolutely possible via an ARMA model. However, my advice
would be to use a state space model and the Kalman filter, which
provide a very flexible, natural and flexible framework for problems
of this type.
-------------------------------------------------------
Riccardo (Jack) Lucchetti
Dipartimento di Scienze Economiche e Sociali (DiSES)
Università Politecnica delle Marche
(formerly known as Università di Ancona)
r.lucchetti(a)univpm.it
http://www2.econ.univpm.it/servizi/hpp/lucchetti
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