* open the birth history data to extract date of birth variables needed.
use "KEBR71FL.DTA", clear

* keep only the variables we need
keep v001 v002 v003 b3 b16
* drop if the child in the birth history was not in the household or not alive 
drop if b16==0 | b16==.
* rename key variables for matching 
rename b16  hvidx
rename v001 hv001
rename v002 hv002
* sort on key variables
sort hv001 hv002 hvidx

* if there are some duplicates of line number in household questionnaire, we need to drop the duplicates
gen dup = (hv001 == hv001[_n-1] & hv002 == hv002[_n-1] & hvidx == hvidx[_n-1])
drop if dup==1
drop dup
* re-sort to make sure still sorted
sort hv001 hv002 hvidx

* save a temporary file for merging
tempfile tempBR
save `tempBR'

* use the PR file for household members for the NAR and GAR indicators
use "KEPR71FL.DTA", clear


* merge in the date of birth from the women's birth history for the household member
merge 1:1 hv001 hv002 hvidx using `tempBR'
* there are a few mismatches of line numbers (typically a small number of cases) coming rom the BR file, so let's drop those
drop if _merge==2

* restrict to de facto household members age 5-24, and drop all others
keep if hv103==1 & inrange(hv105,5,24)

* now we calculate the child's age at the start of the school year
* but first we have to specify the month and year of the start of the school year referred to in the survey
* example, for Zimbabwe 2015 survey this was January 2015
global school_start_yr = 2014
global school_start_mo = 1
* also need the age ranges for primary and secondary
global age_prim_min = 6
global age_prim_max = 13
global age_sec_min = 14
global age_sec_max = 17

* produce century month code of start of school year for each state and phase
gen cmcSch = ($school_start_yr - 1900)*12 + $school_start_mo
replace cmcSch = cmcSch+12 if hv008 >= cmcSch+12
* calculate the age at the start of the school year, using the date of birth from the birth history if we have it
gen school_age = int((cmcSch - b3) / 12) if b3 != .
* Impute an age at the beginning of the school year when CMC of birth is unknown
* the random imputation below means that we won't get a perfect match with the report, but it will be close
gen xtemp = hv008 - (hv105 * 12) if b3 == .
gen cmctemp = xtemp - int(uniform()*12) if b3 == .
replace school_age = int((cmcSch - cmctemp) / 12) if b3 == .

* Generate variables for whether the child is in the age group for primary or seconary school
gen prim_age = inrange(school_age,$age_prim_min,$age_prim_max)
gen sec_age  = inrange(school_age,$age_sec_min ,$age_sec_max )

* create the school attendance variables, not restricted by age
gen prim = (hv122 == 1)
gen sec  = (hv122 == 2)

* set sample weight
cap gen wt = hv005/1000000

* For NAR we can use this as just regular variables and can tabulate as follows, but can't do this for GAR as the numerator is not a subset of the denominator
* NAR is just the proportion attending primary/secondary school of children in the correct age range, for de facto children 
gen nar_prim = prim if prim_age == 1
gen nar_sec  = sec  if sec_age  == 1
lab var nar_prim "Primary school net attendance ratio (NAR)"
lab var nar_sec	"Secondary school net attendance ratio (NAR)"

* tabulate primary school attendance 
tab hv104 nar_prim [iw=wt] , row
tab hv025 nar_prim [iw=wt] , row
tab hv270 nar_prim [iw=wt] , row
* tabulate secondary school attendance 
tab hv104 nar_sec [iw=wt] , row
tab hv025 nar_sec [iw=wt] , row
tab hv270 nar_sec [iw=wt] , row