We have to do a duration model with ens_dur.dta to look for spell to quit smoking and what makes it to reduce. We have made this code, but we dont know what hazard function to specify, or to use a cox hazard. We are just beginners and we have write that, can you help us?

Dataset: https://gofile.io/?c=SL3Jow


Code:
use ens_dur.dta

/*Descriptive Statistics */

des

sum

tab smoker 
tab physical_act
tab bmi
tab health_q
tab d_compl_init
tab d_compl_quit

 /* Drop observations for Ceuta and Melilla */

drop if ccaa>=18

/* Create binary dummies */

gen native=0
replace native=1 if Spanish==1

gen female=0
replace female=1 if sex==2

gen chrill=0
replace chrill=1 if chronic==1

/* Setting the duration and the censoring variables */

stset dur_quit, failure(d_compl_quit)

/* Empirical hazard */

sts graph, hazard

/* Estimation of continuous time duration models */

/* Basic models */

streg, dist(exponential) nohr
streg, dist(weibull) nohr
streg, dist(loglogistic)
streg, dist(lognormal)
streg, dist(ggamma)
streg, dist(gompertz)
stcox, estimate

/* Complete model */ 

streg c.age##c.age female native i.ccaa i.size_mun i.marital_st /*
      */  i.health_q chrill i.bmi i.physical_act, dist(exponential) nohr

streg c.age##c.age female native i.ccaa i.size_mun i.marital_st /*
      */  i.health_q chrill i.bmi i.physical_act, dist(weibull) nohr 
      
streg c.age##c.age female native i.ccaa i.size_mun i.marital_st /*
      */  i.health_q chrill i.bmi i.physical_act, dist(loglogistic) 
      
streg c.age##c.age female native i.ccaa i.size_mun i.marital_st /*
      */  i.health_q chrill i.bmi i.physical_act, dist(lognormal) 
      
streg c.age##c.age female native i.ccaa i.size_mun i.marital_st /*
      */  i.health_q chrill i.bmi i.physical_act, dist(ggamma) 
      
streg c.age##c.age female native i.ccaa i.size_mun i.marital_st /*
      */  i.health_q chrill i.bmi i.physical_act, dist(gompertz) nohr
      
stcox c.age##c.age female native i.ccaa i.size_mun i.marital_st /*
      */  i.health_q chrill i.bmi i.physical_act, nohr      
      
estat phtest