SUBROUTINE IDENT_1 ( D2C, N1, N2, SPACING, PEAK, IMARK, NPTS )
C
C     Decide if this data is on fringe -2, -1, 0, +1, or +2.
C     by chosing the fringe that gives the smallest deviation.
C     
      IMPLICIT UNDEFINED (A-Z)
      INTEGER *4 IMARK(*), I, J, K, NPTS, N1, N2, IFRINGE(5)
      REAL *4 D2C(N1,N2), PEAK(*), CHISQ
      REAL *4 NEWCHI, DELTA1, DELTA2, SPACING(9,2)
      DATA IFRINGE / 0, 1, -1, 2, -2 /
      DO I = 1, NPTS
          DO K = 1, 2
              DELTA1 = ABS( D2C(I,K) - PEAK(K) - SPACING(1,1) )
              DELTA2 = ABS( D2C(I,K) - PEAK(K) - SPACING(1,2) )
          END DO
          CHISQ = MAX ( DELTA1, DELTA2 )
          IMARK(I) = 1
          DO J = 2, 5
              NEWCHI = 0.
              DELTA1 = MIN ( 
     $               ABS( D2C(I,1) - PEAK(1) - SPACING(2*J-1,1) ),
     $               ABS( D2C(I,1) - PEAK(1) - SPACING(2*J-2,1) ) )
              DELTA2 = MIN ( 
     $               ABS( D2C(I,2) - PEAK(2) - SPACING(2*J-1,2) ),
     $               ABS( D2C(I,2) - PEAK(2) - SPACING(2*J-2,2) ) )
              NEWCHI = MAX( DELTA1, DELTA2 )
              IF ( NEWCHI .LT. CHISQ ) THEN
                  IMARK(I) = J
                  CHISQ = NEWCHI
              END IF
          END DO
          IMARK(I) = IFRINGE(IMARK(I))
      END DO
      RETURN
      END