cd "C:\Users\ssarma2\Documents\Teaching\Winter 2014\Lectures\Survival Analysis\Extraction from KM"

use Example


/*Step 1: declare the data as count-time data by informing STATA key variables: time, events, censored*/
ctset time_month n_events n_censored

/*Step 2: Convert count-time data to survival-time data using cttost command*/
cttost 
save Example_ct

/*Step 3: Check your K-M curve -- should appear close to the published K-M curve*/
sts graph 


/*Fit a Weibull Distribution*/
streg, dist(weibull) time nohr

/*Weibull shape parameter gamma=p*/
/*Weibull scale parameter lambada that SAS produces is exp(_cons) in STATA*/

/*Compare estimators*/
streg, dist(exp)
estimates store exp
streg, dist(weib)
estimates store weib
streg, dist(lnormal)
estimates store lnorm
streg, dist(gomp)
estimates store gomp
streg, dist(gamma)
estimates store gamma

estimates stats _all


/*generalized gamma model*/

streg, dist(gamma) time

/*log-normal*/
test [kappa]_b[_cons]=0

streg, dist(gamma) time
lrtest, saving(0)

streg, dist(lnormal) time
lrtest, force

/*Weibull*/
streg, dist(gamma) time
test [kappa]_b[_cons]=1


/*Exponential*/
streg, dist(gamma) time
test [kappa]_b[_cons]=0, notest
test [ln_sig]_b[_cons]=0, accum