* A simple program for computing group means (P) and 
* deviations from group means (Q).
capture program drop PQ
program define PQ
version 4.0
	local options "Level(integer $S_level)"
	local varlist "req ex"
	parse "`*'"
	parse "`varlist'",parse(" ")
		sort id
		quietly by id: gen P`1'=sum(`1')/sum(`1'~=.) 
		quietly by id: replace P`1'=P`1'[_N]      
		quietly gen Q`1'=`1'-P`1'
end