;;;; Evett's 1994 algorithm for determining LRs

(load "utests.lisp")

(deftest naive-evett94-test ()
	"Performs a test for Evett's 1994 naive algorithm."
	(check
		(= 525.02 (naive-evett94))
	)
)

(defun naive-evett94 
	(&optional &key
		(n 4)
		(p-values #(.25 .22 .14 .14 .069 .064 .033 .033 .022 .02 .013))
		(s-values #(.728 .166 .065 .018 .018 .006))
		(t-values #(.02 .075 .145 .195 .195 .155 .105 .06 .03 .01 .005))
		(f-value .03)
	)
	"Performs the naive algorithm for determining the LR using
	data supplied by the LHS survey."
	(+ (/ (* (elt p-values 0) (elt t-values n)) (* (elt p-values 1) (elt s-values n) f-value)) (elt t-values 0))
)

(deftest test-evett94 ()
	"Performs a test for Evett's 1994 algorithm."
	(check
		( = 20.357302 (evett94) )
	)
)

(defun evett94
	(
		&optional
		&key
			(z 1)
			(n 1)
			(p-values #(.41 .28 .13 .1 .05 .02 .01 .005))
			(s-values #(.70 .18 .08 .025 .015))
			(t-values #(.02 .075 .145 .195 .195 .155 .105 
.06 .03 .01 .005))
			(f-value .03)
	)
	"Performs the algorithm for determining the LR using
	data supplied by the LHS given a factor of z, and a
	number of fragments on clothing n."
	(/ (+ (* (elt t-values 0) (elt p-values 1) (elt s-values n) 
f-value) (* (elt t-values n) (elt p-values 0))) (* (elt p-values 1) (elt 
s-values n) f-value))
)