categorical variables in gvselect

[Gianfranco Di Gennaro]

Dear all, thanks in advance.

I’m trying to run the best subset command "gvselect" and I wonder how to introduce the categorical variables.
If I try to introduce i.categoricalvariable in the varlist I get the error "factor-variable and time-series operators not allowed".

At this regard in the help- I don't see any explanation.

Thanks again.
Gianfranco

[Andrew Musau]

I am not familiar with this command, but probably it predates factor variables. As stated in the FAQ Advice #12, you need to state the provenance of community-contributed commands that you reference. Before factor variables, you would use the -xi- prefix or generate the indicators yourself.

sysuse auto, clear
xi: regress mpg i.rep78
tabulate rep78, gen(repair)
regress mpg repair2-repair5

[Ope Abiodun]

Hello Statalisters,

I am using gvselect from SSC in Stata 13.1. I tried introducing categorical variables in gvselect using the xi prefix after running a logistic regression and got the response and error below. The variables without the i. prefix are continuous. I don't know the reason for this error. Thanks in advance for your help.

logit hosp pce i.usctyp i.chr_id i.sex i.wealth_cat1 i.caste i.marst i.edu2 i.emp2 i.tobac i.relig i.comorb i.insur ageyr_c diag_mo q402_0_ , vce(cluster village)

xi: gvselect <term> pce ageyr_c diag_mo q402_0_ i.usctyp i.chr_id i.sex i.wealth_cat1 i.caste i.marst i.edu2 i.emp2 i.tobac i.relig i.comorb i.insur , nmodels(2) : logit hosp <term>

i.usctyp _Iusctyp_1-2 (naturally coded; _Iusctyp_1 omitted)
i.chr_id _Ichr_id_1-5 (naturally coded; _Ichr_id_1 omitted)
i.sex _Isex_1-2 (naturally coded; _Isex_1 omitted)
i.wealth_cat1 _Iwealth_ca_1-5 (naturally coded; _Iwealth_ca_1 omitted)
i.caste _Icaste_1-3 (naturally coded; _Icaste_1 omitted)
i.marst _Imarst_2-3 (naturally coded; _Imarst_2 omitted)
i.edu2 _Iedu2_1-2 (naturally coded; _Iedu2_1 omitted)
i.emp2 _Iemp2_1-2 (naturally coded; _Iemp2_1 omitted)
i.tobac _Itobac_1-2 (naturally coded; _Itobac_1 omitted)
i.relig _Irelig_1-2 (naturally coded; _Irelig_1 omitted)
i.comorb _Icomorb_0-1 (naturally coded; _Icomorb_0 omitted)
i.insur _Iinsur_0-1 (naturally coded; _Iinsur_0 omitted)

138 observations containing missing predictor values

varlist not allowed
r(101);