Am 28.02.2024 um 21:33 schrieb Brian Revell:
 So back to my original question. How to prevent The Forecast graphic
 treating the Panel data series as a continuum between panels, and 
 joining panel units together.
 Brian 
OK, so from what I understand you're running a fixed-effects model by 
using the explicit LSDV approach, in order to "trick" gretl's pooled OLS 
routine to show you something.
Econometrically I'd say that this requires a reasonably large time 
dimension; in a short-T panel you cannot consistently estimate the 
unit-specific intercepts. It sounded as if for you T=21, so it might 
possibly just be enough. I'm also assuming that you only have exogenous 
regressors, especially no lagged dependent variables.
Technically I'm not aware of an easy way to obtain this plot, currently. 
It is feasible, because you can save the static forecast values and its 
standard errors, and then you could construct a plot of the various 
units in the time series dimension. In the latest gretl version (2023c) 
there is a new feature that allows to plot several bands in a single 
plot, which would be needed here. (There have been some bug fixes in 
that area since 2023c was released, not sure if those fixes would be 
needed as well.) But it would involve some scripting, would admittedly 
be a little fiddly and not completely trivial.
I challenge our practical panel guy Artur to present a solution, hehe!
cheers
sven