program define zoib_beta_lf
	version 8.2
	args lnf proportion ln_phi
	tempvar mu muprime phi

	quietly gen double `mu' = invlogit(`proportion')
	quietly gen double `muprime' = invlogit(-`proportion')
	quietly gen double `phi' = exp(`ln_phi')

	quietly replace `lnf' =   ///
	        lngamma(`phi') - lngamma(`mu'*`phi')-lngamma(`muprime'*`phi') ///
                + (`mu'*`phi'-1)*ln($ML_y1) +(`muprime'*`phi'-1)*ln(1-$ML_y1) 
end