jack schrieb:
On Sat, 14 Jan 2006, Allin Cottrell wrote:
> Makes sense. I too have a vague recollection of how PcGive does it,
> but -- apart from the issue of gretl's regressor selection
> sub-window becoming overcrowded -- I feel that gretl's selector is
> easier to use.
In PcGive, you select a variable, alter (if change is needed) the number of lags in an
entry field,
and add the bunch to the list of regressors. (Afterwards you can delete individual
intermediate lags
or the contemporaneous original variable itself if you want to.)
The advantages over gretl are imho:
- needed lags are created on-the-fly
- less clutter/noise in the list of selectable variables
A slight disadvantage could be that if you only want some non-contiguous lags, it might be
a little
more click-work than in gretl.
Overall I think it's worth imitating.
I also think there is a slight problem with the current state of affairs; imagine you want
to run a
quasi-dynamic regression:
x_t = c + b y_{t-1} + u_t
(One reason for that formulation could be to avoid simultaneity bias that could arise when
you
include contemporaneous y_t instead.)
Doing that in gretl is possible, but since y_{t-1} is not visible in the main window, it
might
become slightly annoying to open the regression dialog, see that y_{t-1} does not yet
exist, cancel
the dialog, create y_{t-1}, go back to the dialog. Secondly, in this scenario you might
want to
graph x_t against y_{t-1}, which is difficult because lags are not selectable in the main
window.
So the solution would be (I think): First adopt the on-the-fly lag creation, and thus tell
the users
that explicitly creating lags is normally unnecessary => no clutter in the main window.
Second, make
created lags visible again in the main window to have them easily available for graphing,
see above.
If someone stubbornly refused to use the console or scripts, we could have
a menu item like "Create list with lags" (possibly right-clickable). Then
the list containing the wanted lags appears as if it was a single series,
and it can be included in the regression.
This approach would become unnecessary after the above imitation of PcGive's behavior,
wouldn't it?
Just my 2c
Cheers,
Sven