*! version 1.0.1  8Mar93 Royston; STB-12 sg1.5
program define nlexp2
	version 3.0
	if "`1'"=="?" {
		mac def S_2 "2-param. exp. growth curve, $S_E_depv=b1*b2^`2'"
		mac def S_1 "b1 b2"
/*
	Approximate initial values by regression of log Y on X.
*/
		local exp "[$S_E_wgt $S_E_exp]"
		tempvar Y
		quietly {
			gen `Y' = log($S_E_depv) $S_E_if $S_E_in
			reg `Y' `2' `exp'
		}
		mac def b1 = exp(_b[_cons])
		mac def b2 = exp(_b[`2'])
		exit
	}
	replace `1'=$b1*$b2^`2'
end