C+
C NAME:
C	ArrR4Interpolate
C PURPOSE:
C	Interpolate on 1-dim real*4 array.
C CALLING SEQUENCE:
	function ArrR4Interpolate(N,A,X)
C INPUTS:
C	N	integer		# points in array
C	A(N)	real		Array of function values 
C	X	real		Function value where interpolated position is needed
C OUTPUTS:
C	ArrR4Interpolate
C		real		interpolated index in [1,N]
C				A BadR4 value is returned if X lies outside the
C				range of input array A.
C CALLS:
C	BadR4
C RESTRICTIONS:
C	A must be a monotonically increasing array.
C PROCEDURE:
C	For given X the pair of indices I-1 and I are located
C	where A(I-1) < X <= A(I). Then a linear interpolation between these
C	two points gives the return floating point index.
C MODIFICATION HISTORY:
C	SEP-2002, Paul Hick (UCSD/CASS; pphick@ucsd.edu)
C-
	    integer	N
	    real	A(*)
	    real	X

	if (A(1) .le. X .and. X .le. A(N)) then

	    I = 1
	    do while (I .le. N .and. X .gt. A(I))
		I = I+1
	    end do

	    ArrR4Interpolate = float(I)
	    if (I .ne. 1) ArrR4Interpolate = ArrR4Interpolate-(X-A(I))/(A(I-1)-A(I))

	else

	    ArrR4Interpolate = 	BadR4()

	end if

	return
	end