*# dat # {cmd:not duplicate} - Simple, yet hard to describe - shows the ways in which records are not duplicate # help
*! 7oct2009 
program nodup 
version 8.2 
syntax [varlist] [if],dup(varlist) [over(integer 2)] 
 
local varlist :list varlist-dup 
preserve 
capture keep `if' 
tempvar tag subg subsum submiss 
qui duplicates tag `dup',g(`tag') 
qui keep if `tag' 
qui count 
if `r(N)'==0 { 
	di "{txt:No duplicates}" 
	exit 
	} 
drop `tag' 
egen `tag'=tag(`dup'), missing 
qui count if `tag' 
local sets= r(N) 
qui count if `tag' & mi(`=subinstr("`=trim("`dup'")'"," ",",",.)') 
local setsmiss= r(N) 
mata: out=J(0,4,"") 
foreach v of varlist `varlist' { 
	egen `subg'=tag(`v' `dup'), missing 
	bysort `dup': egen `subsum'=sum(`subg') 
	qui count if `subsum'>1 & `tag' 
	if `r(N)' { 
		mata: out=out\"`v'","`r(N)'","","" 
		bysort `dup': egen `submiss'=sum(`subg'&mi(`v')) 
		qui count if `subsum'>1 & `tag' & `submiss'==0 
		mata: out[rows(out),3]="`r(N)'" 
		qui count if `subsum'>`over' & `tag' 
		mata: out[rows(out),4]="`r(N)'" 
		drop `submiss' 
		} 
	drop `subg' `subsum' 
	} 
di 
di "{txt:Duplicates by `dup':} {res:`sets' sets, `setsmiss' w/missing}" _n
mata: table=table_createM(("Sets differing by","N","N w/o .",">`over' vals")\out)
mata: asarray(table,"head",1)
mata: table_code(table,"vline","t",1,"thick")
mata: table_present(table)
end