*! version 1.0.0  18Jan93 Royston; STB-11 sg1.4
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 $S_E_in
                        reg `Y' `2'
                }
                mac def b1 = exp(_b[_cons])
                mac def b2 = exp(_b[`2'])
                exit
        }
        replace `1'=$b1*$b2^`2'
end