---------------------------------------------------------------------------------------
      name:  <unnamed>
       log:  C:\MyDocs\MPH\LectureNotes\ClassDoLogData\Poisson\8.8.2.Survival_to_Person
> Years.log
  log type:  text
 opened on:  22 Jan 2010, 14:56:03

. *  8.8.2.Survival_to_PersonYears.log
. *
. *  Convert survival data to person-year data.
. *  The survival data set must have the following variables:
. *      id      = patient id,
. *      age_in  = age at start of follow-up,
. *      age_out = age at end of follow-up,
. *      fate    = fate at exit:  censored = 0, dead = 1,
. *      treat   = treatment variable.
. *
. *  The person-year data set created below will contain one
. *  record per unique combination of treatment and age.
. *
. *  Variables in the person-year data set that must not be in the
. *  original survival data set are
. *      age_now = an age of people in the cohort,
. *      pt_yrs  = number of patient-years of observations of people
. *                who are age_now years old, 
. *      deaths  = number of events (fate=1) occurring in pt_yrs of 
. *                follow-up for this group of patients.
. *
. use C:\WDDtext\8.8.2.Survival.dta, clear

. list

     +--------------------------------------+
     | id   age_in   age_out   treat   fate |
     |--------------------------------------|
  1. |  A        1         4       1      0 |
  2. |  B        3         5       1      1 |
  3. |  C        3         6       2      0 |
  4. |  D        2         3       2      1 |
  5. |  E        1         3       2      1 |
     +--------------------------------------+

. generate exit = age_out + 1

. stset exit, id(id) enter(time age_in) failure(fate)

                id:  id
     failure event:  fate != 0 & fate < .
obs. time interval:  (exit[_n-1], exit]
 enter on or after:  time age_in
 exit on or before:  failure

------------------------------------------------------------------------------
        5  total obs.
        0  exclusions
------------------------------------------------------------------------------
        5  obs. remaining, representing
        5  subjects
        3  failures in single failure-per-subject data
       16  total analysis time at risk, at risk from t =         0
                             earliest observed entry t =         1
                                  last observed exit t =         7

. stsplit age_now, at(0(1)6)
(11 observations (episodes) created)

. list  id age_in age_out treat fate exit age_now

     +-------------------------------------------------------+
     | id   age_in   age_out   treat   fate   exit   age_now |
     |-------------------------------------------------------|
  1. |  A        1         4       1      .      2         1 |
  2. |  A        1         4       1      .      3         2 |
  3. |  A        1         4       1      .      4         3 |
  4. |  A        1         4       1      0      5         4 |
  5. |  B        3         5       1      .      4         3 |
     |-------------------------------------------------------|
  6. |  B        3         5       1      .      5         4 |
  7. |  B        3         5       1      1      6         5 |
  8. |  C        3         6       2      .      4         3 |
  9. |  C        3         6       2      .      5         4 |
 10. |  C        3         6       2      .      6         5 |
     |-------------------------------------------------------|
 11. |  C        3         6       2      0      7         6 |
 12. |  D        2         3       2      .      3         2 |
 13. |  D        2         3       2      1      4         3 |
 14. |  E        1         3       2      .      2         1 |
 15. |  E        1         3       2      .      3         2 |
     |-------------------------------------------------------|
 16. |  E        1         3       2      1      4         3 |
     +-------------------------------------------------------+


end of do-file


. help collapse

. collapse (count) pt_yrs =  age_in (sum) deaths = fate, by(treat age_now)

. list

     +-----------------------------------+
     | treat   age_now   pt_yrs   deaths |
     |-----------------------------------|
  1. |     1         1        1        0 |
  2. |     1         2        1        0 |
  3. |     1         3        2        0 |
  4. |     1         4        2        0 |
  5. |     1         5        1        1 |
     |-----------------------------------|
  6. |     2         1        1        0 |
  7. |     2         2        2        0 |
  8. |     2         3        3        2 |
  9. |     2         4        1        0 |
 10. |     2         5        1        0 |
     |-----------------------------------|
 11. |     2         6        1        0 |
     +-----------------------------------+

. list

     +-----------------------------------+
     | treat   age_now   pt_yrs   deaths |
     |-----------------------------------|
  1. |     1         1        1        0 |
  2. |     1         2        1        0 |
  3. |     1         3        2        0 |
  4. |     1         4        2        0 |
  5. |     1         5        1        1 |
     |-----------------------------------|
  6. |     2         1        1        0 |
  7. |     2         2        2        0 |
  8. |     2         3        3        2 |
  9. |     2         4        1        0 |
 10. |     2         5        1        0 |
     |-----------------------------------|
 11. |     2         6        1        0 |
     +-----------------------------------+

. exit, clear