Stata program to get relative humidity given temperature and dew point

gen_relative_humidity.ado

program define gen_relative_humidity
	* Calculate relative humidity given dry bulb temperature and dew point
	syntax, DRYbulbtemp(varname) DEWpoint(varname) [GENerate(string)]
	* Inputs in F
	local T `drybulbtemp'
	local TD `dewpoint'

	if "`generate'" == "" {
		local generate "rel_humidity"
	}

	capture drop `generate'

	* Calculate relative humidity from dry bulb temperature and humidity
	* http://andrew.rsmas.miami.edu/bmcnoldy/Humidity.html
	tempvar TC TDC
	gen `TC' = (5/9) * (`T' - 32)
	gen `TDC' = (5/9) * (`TD' - 32)

	gen `generate' = 100*(exp((17.625*`TDC')/(243.04+`TDC'))/exp((17.625*`TC')/(243.04+`TC')))
end