cd C:\StataData\LDA

use nepal.dta, replace

sort id age

** generate visit/time
by id: gen time=_n

** generate gappy time.
by id: gen timeGappy=_n if id <101
by id: replace timeGappy=_n+1 if id >100

** change spacing within individuals
by id: gen timeDisplace=_n if id <101
by id: replace timeDisplace=_n+1 if id >100
by id: replace timeDisplace=9 if timeDisplace ==6
by id: replace timeDisplace=7 if timeDisplace ==5



**Remove observations with weight above 80kg (Q2-4 I used this dataset)
drop if (wt>80)

**Or, code observations with weight above 80kg as missing
replace wt=. if wt>80

** prais requires tsset
** only run one of the tsset.
** then continue to praise and 
** xtregar command below.
tsset id time
tsset id timeGappy
tsset id timeDisplace





** serially correlated data...(slide 39 lecture 6)
prais arm wt age sex

matrix list e(b)
display e(rho)
matrix list e(V)

** random intercept plus serial correlation (slide 42 lecture 6)
xtregar arm wt age sex