FUNCTION locate(xx,x)
	USE nrtype
	IMPLICIT NONE
	REAL(SP), DIMENSION(:), INTENT(IN) :: xx
	REAL(SP), INTENT(IN) :: x
	INTEGER(I4B) :: locate
	INTEGER(I4B) :: n,jl,jm,ju
	LOGICAL :: ascnd
	n=size(xx)
	ascnd = (xx(n) >= xx(1))
	jl=0
	ju=n+1
	do
		if (ju-jl <= 1) exit
		jm=(ju+jl)/2
		if (ascnd .eqv. (x >= xx(jm))) then
			jl=jm
		else
			ju=jm
		end if
	end do
	if (x == xx(1)) then
		locate=1
	else if (x == xx(n)) then
		locate=n-1
	else
		locate=jl
	end if
	END FUNCTION locate