*! PERSON-YEAR / GROUP FAILURE CALCULATOR        
*! Joseph Hilbe, STB   1/22/92
*
*  pyears <dob> <begin> <end>, i(<interval>) g(<groups>) s(<start-age>)                        
*               **** variables in SAS years only ****

program define pyears
  version 3.0
  local varlist "req ex min(3)"
  local options "`options' Interval(integer 5) Group(integer 4) Start(integer 30) List  Dead"
  parse "`*'"
  parse "`varlist'", parse(" ")
  
qui {
cap drop grp*
cap drop ingrp*
cap drop pyr*
cap drop num*

tempvar sasdob bsas esas

gen `sasdob'=`1'
gen `bsas'  =`2'
gen `esas'  =`3'

local inter=`interval'
local group=`group'
local start=`start'
local restart=`start'

tempvar todrop
egen int `todrop'=rmiss(`varlist')
drop if `todrop'
drop `todrop'

replace `bsas' = `sasdob'+(365.25 * `start') if `bsas'< (`sasdob'+(365.25*`start'))
#delimit ;
replace `esas' = (`sasdob'+(365.25*`start'+(`inter'*`group'*365.25))) 
     if `esas' > (`sasdob'+(365.25*`start'+(`inter'*`group'*365.25)));
#delimit cr

local i=1
while `i'<=`group'  {
  gen grp`i'b=`sasdob'+(365.25*`start')
  gen grp`i'e=`sasdob'+(365.25*(`start'+`inter'))-1
  gen num`i'=1 if `esas' >= grp`i'b & `esas'<= grp`i'e
  gen numa`i'=1 if `bsas'>= grp`i'b & `bsas'<= grp`i'e
  local i=`i'+1
  local start=`start'+`inter'
}

gen ingrp1=(`esas'-`bsas')*.00273785 if `bsas'<grp1e & `esas'<grp1e
replace ingrp1=(grp1e-`bsas')*.00273785 if `bsas'<grp1e & `esas'>grp1e

local i=2
local j=1
while `i'< `group' {
 #delimit ;
 gen ingrp`i'=(365.25*5)*.00273785 if ingrp`j'~=. & `esas'>grp`j'e & 
              `bsas'>grp1b & `bsas'<grp`j'e;
 #delimit cr
 replace ingrp`i'=(grp`i'e-`bsas')*.00273785 if ingrp`j'==. & `bsas'<grp`i'e
 replace ingrp`i'=(`esas'-grp`i'b)*.00273785 if `esas'<=grp`i'e & `esas'>grp`i'b
 replace ingrp`i'=(`esas'-`bsas')*.00273785 if `bsas'>grp`i'b & `esas'<=grp`i'e
   local i=`i'+1
   local j=`j'+1
}

local i=`group'
#delimit ;
gen ingrp`i'=(`esas'-grp`i'b)*.00273785 if `bsas'<grp`i'b & `esas'<grp`i'e & 
   !(`esas'<grp`i'b);
#delimit cr
replace ingrp`i'=(`esas'-`bsas')*.00273785 if `bsas'>grp`i'b

local i=1
while `i'<=`group' {
  egen pyr`i'=sum(ingrp`i')
  egen numd`i'=sum(num`i') if `4'==1
  egen nums`i'=sum(num`i')
  egen numb`i'=sum(numa`i')
  local i=`i'+1
}
}

if "`list'"!="" {
  di _n(1)
  di in gr " Listing of Casewise Person-years"
  di " --------------------------------"
  l ingrp*
}

if "`dead'"=="" {
 di _n(2)
 di in gr " Person-years Totals per Age Division"
 di " ------------------------------------"
 local i=1
 local range=`inter'-1
 local rnge =`restart'+`range'

 while `i'<=`group'  {
  di in gr " Grp  `restart' - `rnge'   => " in ye %12.4f pyr`i'
  local i=`i'+1
  local restart=`restart'+`inter'
  local rnge = `restart'+`range'
 }
}

if "`dead'"!="" {
di _n(2)
di in gr " Person-years:          Totals      Enter      End    Failures   "
di " -------------------------------------------------------------"
local i=1
local range=`inter'-1
local rnge =`restart'+`range'

while `i'<=`group'  {
 #delimit ;
 di in gr " Grp  `restart' - `rnge'   => " in ye _col(20) %12.4f pyr`i'    
    _col(41)  numb`i' _col(50)  nums`i' _col(59) numd`i';
 #delimit cr
 local i=`i'+1
 local restart=`restart'+`inter'
 local rnge = `restart'+`range'
}
}

cap drop grp*
cap drop ingrp*
cap drop pyr*
cap drop num*

end