[Gretl-users] Suggestions for new features and some changes in gretl
Dear gretl developers,
During the last months I have taught a course in Applied
econometrics, where the students have written four exam papers
analysing real economic data using gretl 1.6.0.
After my and my students experiences with using gretl for this
course, I have the following suggestions for new features in gretl:
* Add a menu entry for creating cross tabulation tables, for cross
tabulation of one variable against the other
* Add the possibility to calculate bootstrapped confidence intervals
for OLS estimates.
* For OLS output, also show the ANOVA table (or add a check box where
the user can choose to show the ANOVA table in the output)
For the augmented Augmented Dickey-Fuller test, regarding the
"testing-down algorithm" for choosing lag length, it says in the help
file: "In the context of step 2 above, 'significant' means that the
t-statistic for the last lag has an asymptotic two-sided p-value,
against the normal distribution, of 0.10 or less."
Suggestion:
* Include an option where the user can specify the value of the
asymptotic two-sided p-value himself, so the user is not stuck with
the 0.10 value
* Add the possibility to automatically choose the lag length based on
Akaike Information Criterion (AIC), Schwarz Bayesian criterion (BIC)
or Hannan-Quinn criterion (HQC) (possibly by using a drop down list
where the user can choose which method to use) instead of only
testing if the lags are significant. This possibility should of
course also be included in the Engle-Granger cointegration test.
After estimating a model and choosing "Tests > Collinearity" from the
output window, the variance infation factors (VIF) are given. Suggestion:
* Also show the value of the determinant of X'X as a measure of
multicollinearity (see, e.g., Montgomery et al., Introduction to
Linear Regression Analysis, Wiley: 2006, p. 340)
Some suggestions for cosmetic changes:
* Move the "Augmented Dickey-Fuller test" and "KPSS test" into a new
submenu entry "Variable > Unit root test", as follows: "Variable >
Unit root test > Augmented Dickey-Fuller test" and "Variable > Unit
root test > KPSS test"
* When adding Logs of selected varaibles call it ln_x or log_x
instead of l_x, in line with the use of sq_x. It makes it easier to
see what the variable is.
* In the outputs decimals (,) are used as separators (e.g., 3,14),
but for input one have to use a full stop (.) as separator (e.g.,
3.14). This is somwehat unintuitive, and should be changed so that
the same is used for output and input.
Some other suggestions for new features: Add menu entries for calculating
*1-sample sign test
*1-sample Wilcoxon signed rank test
*2-sample Wilcoxon rank sum test
If these latter tests are added, then create a new submenu
"Variable > Nonparametric tests" where the Runs test, the 1-sample
sign test, 1-sample Wilcoxon signed rank test and 2-sample Wilcoxon
rank sum test are placed.
Finally, thanks for a really great software. The students really liked it.
Best regards,
Andreas Karlsson,
Uppsala University,
Sweden