Re: [Gretl-users] GRETL - User Suggestions - Minus Signs and Binary Logit Function options
by Riccardo (Jack) Lucchetti
On Fri, 5 May 2017, Rao G.V. wrote:
> Hi Riccardo
>
> I got your details from the GRETL user community site. A great friendly
> product from a user perspective!
Thank you. I'm taking the liberty to forward my reply to the gretl user
list, so that our exchange becomes public and possibly useful to other
people too.
> I have used a number of functions but mainly the logit regression and
> the Bayesian function. All good.
>
> However I noted that when the output for the logit function is saved in
> word and copied to an excel spreadsheet the signs are not proper minus
> signs. See below.
>
>
> GRETL OUTPUT
>
> Coefficient Std. Error z p-value
> V3D_A1_6 −175812 50541.4 −3.479 0.0005 ***
>
>
> compared to
>
> -175812
>
> -3.479
>
> Which means one needs to correct the output if further analytical work
> needs to be performed. Now, in an earlier version of GRETL the signs
> were in the correct format !............ so may be a suggestion to
> correct this. The sign has remained unchanged for quite some time now.
This has come up several times. If you copy-n-paste from gretl to a text
processing application we use a character that is the typographically
appropriate glyph for the minus operator, which is unfortunately different
from the minus sign that mathematical apps use. However, if you
copy-n-paste directly from gretl to a spreadsheet (without the
intermediate word processing passage) everything should be ok.
> Another suggestion would be to add a stepwise function (backward or
> forward) for sequential addition/deletion of variables to determine the
> final logit model (example in the binary logit) with the existing
> p-values (say 0.1) as the criteria of adding (or removing) significant
> variables. This is similar to functions/options available in SPSS,
> Statgraphics, Stata and other packages. This would greatly assist a
> user identify the significant variables and model quicker.
>
> Admittedly this will add to the processing time and memory to the final
> output. However it will definitely be a big improvement and if it is
> added to the binary logit function as an option in the menu like other
> software packages (compared to a separate function package) even
> better!. Currently this is a very manual repetitive process of removing
> each non-significant variable from the model, especially if the list of
> regressors is large and therefore time consuming.
>
> I noted that there is a function package available for sequential
> variables, however this is only for OLS not other functions such as
> binary logit. Also the function seems to require a list 1 of initial
> regressors and then the candidates. What if all regressors are
> candidates to begin with......Also there does not appear to be p-value
> criteria which is a standard feature in most packages.
Actually, the existing function package could be extended to cover a wider
class of models than OLS. Let me think about it.
> I hope my input is useful
It surely is. Thank you for your feedback!
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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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