[Gretl-devel] Re: weird list creation behavior in package GUI (model window context)

On Sun, 6 Apr 2025, Sven Schreiber wrote: Thanks for the report. So Sven has in mind a function package which offers attachment to the "Analysis" menu in a gretl model window. It's intended to perform an action for which a particular list of series is needed, namely, the list of regressors for the model in question, minus any lags of the dependent variable (and also minus the constant). A function in this context has access to the $model accessor and Sven wishes to construct the needed list thus: bundle mod = $model list Lexo = mod.xlist - lags(mod.maxlag, mod.ylist) - const where the call "lags(mod.maxlag, mod.ylist)" is meant to create the lagged dependent list to subtract from mod.xlist, which contains all the regressors. Now here's the dataset context in the example Sven describes. * The "denmark" dataset contains the four series LRM, LRY, IBO and IDE, with IDs 1 to 4. * A regression of the form "ols LRM const IBO LRM(-1 to -2)" is run, which results in the addition to the dataset of the lags LRM_1 and LRM_2, with series IDs 5 and 6. So mod.xlist holds "1 0 3 5 6" and the lagged dependent list is the subset "5 6". Now what happens when the packaged function is called? It turns out that the call "lags(mod.maxlag, mod.ylist)" results in the (re-)creation of the two LRM lags, appended to the dataset as series 7 and 8. The original versions, under IDs 5 and 6, are not "visible" within the function because they were not passed as arguments (nor via a standard list, but just inside a bundle). So the list subtraction doesn't work: gretl tries to drop series 7 and 8 from mod.xlist, but they're not present. It seems that it ought to be possible to ensure that when a list-containing bundle is passed as a function argument, the listed series become "visible" -- then Sven's approach would work. However, in the meantime here's an approach that does work. We define a helper function as follows <hansl> function list exog_list (list xlist, list ylist) string yl = varnames(ylist)[1] ~ "_" strings xnames = varnames(xlist) list drop loop i=1..nelem(xlist) if strstr(xnames[i], yl) != "" drop += xlist[i] endif endloop list Lexo = xlist - drop - const return Lexo end function </hansl> and in the primary function we do bundle mod = $model list Lexo = exog_list(mod.xlist, mod.ylist) Allin