/********************************************************************
link2.do

Written by Russell Dimond 10/2002 for Intermediate Stata Class

Uses the map created in part one to link a person's data with their
mother's data.

********************************************************************/
clear
capture log close
set more off
log using link2,text replace

use link
gen id=mother
sort id
merge id using map
/* 
Note that we are merging an observation with that observation's
mother from the map! Thus obsNum is the mother's obsNum.
*/
drop if _merge==2
/*
_merge==2 means observations from map that weren't matched with 
a person from the original data because their mother isn't in the
data set. Thus they are duplicates.
*/
sort person
ren obsNum momsObsNum
label var momsObsNum "Observation number of Mother when sorted by person"
drop id _merge

gen diff=age[momsObsNum]-age

save link2,replace

log close