*! version 1.1.0, feb 98, Guy van Melle  STB-45 gr30
*!
*! function declaration for bivariate normal density
*! to be represented via <hidlin> or <altitude>
*!
*! call: hlbivnor x y z [in L1/L2]
*! x y any two existing vars
*! z created as or replaced by specified values
*!
prog def hlbivnor
*
	loc x `1'
	loc y `2'
	loc z `3'
	cap confirm var `z'
	if _rc {qui gen `z'=.}
	mac shift 3
	loc in "opt"
	parse "`*'"

*--- actual start of function declaration ---

	if "$rho"=="" { glo rho 0 }
	loc r = 1 - ($rho)^2                /* need parentheses !!! */
	loc c = 2 * _pi * sqrt(`r')
	#delimit ;
	qui replace `z'= 
		exp( -(`x'^2 -2*$rho*`x'*`y'+`y'^2) / (2*`r') )/ `c' `in'
	; #delimit cr 
end
*