Re: [Gretl-users] Retrieving the roots of an ARIMA

On 01/31/2012 09:13 PM, Allin Cottrell wrote: > On Tue, 31 Jan 2012, Henrique Andrade wrote: > >> Is there any way to retrieve the roots of an ARIMA model? Is there an >> accessor that allows this kind of operation? > > They are attached to the model in question under the name > "roots". While there is no "$roots" accessor as such, it's now > possible to retrieve them (in CVS and snapshots) via the > special form $["roots"]. This form will work for any named > data attached to the last model in the form of a scalar, > series or matrix. Example: > > open data9-7 > arma 1 2 ; QNC > matrix r = $["roots"] > r > > This form treats the last model as if it were a "bundle", from > which any suitable named data can be extracted. Ho ho -- hold it :-) Seriously, isn't this new syntax being introduced a little hastily? So far everything that could be accessed got its $-accessor. This $[] thing seems to be all new. I'm not saying it's bad, but it seems to exist in parallel to the old-style accessor. After all, all existing accessors could now be re-defined, for example $coeff -> $["coeff"]. Maybe that's the way to go (old-style accessors could be kept as syntactic sugar for backward-compatibility).