SUBROUTINE DPCHCI(N,H,SLOPE,D,INCFD)
C***BEGIN PROLOGUE  DPCHCI
C***REFER TO  DPCHIC
C***ROUTINES CALLED  DPCHST
C***REVISION DATE  870707   (YYMMDD)
C***DESCRIPTION
C
C          DPCHCI:  DPCHIC Initial Derivative Setter.
C
C    Called by DPCHIC to set derivatives needed to determine a monotone
C    piecewise cubic Hermite interpolant to the data.
C
C    Default boundary conditions are provided which are compatible
C    with monotonicity.  If the data are only piecewise monotonic, the
C    interpolant will have an extremum at each point where monotonicity
C    switches direction.
C
C    To facilitate two-dimensional applications, includes an increment
C    between successive values of the D-array.
C
C    The resulting piecewise cubic Hermite function should be identical
C    (within roundoff error) to that produced by DPCHIM.
C
C ----------------------------------------------------------------------
C
C  Calling sequence:
C
C        PARAMETER  (INCFD = ...)
C        INTEGER  N
C        DOUBLE PRECISION  H(N), SLOPE(N), D(INCFD,N)
C
C        CALL  DPCHCI (N, H, SLOPE, D, INCFD)
C
C   Parameters:
C
C     N -- (input) number of data points.
C           If N=2, simply does linear interpolation.
C
C     H -- (input) real*8 array of interval lengths.
C     SLOPE -- (input) real*8 array of data slopes.
C           If the data are (X(I),Y(I)), I=1(1)N, then these inputs are:
C                  H(I) =  X(I+1)-X(I),
C              SLOPE(I) = (Y(I+1)-Y(I))/H(I),  I=1(1)N-1.
C
C     D -- (output) real*8 array of derivative values at data points.
C           If the data are monotonic, these values will determine a
C           a monotone cubic Hermite function.
C           The value corresponding to X(I) is stored in
C                D(1+(I-1)*INCFD),  I=1(1)N.
C           No other entries in D are changed.
C
C     INCFD -- (input) increment between successive values in D.
C           This argument is provided primarily for 2-D applications.
C
C    -------
C    WARNING:  This routine does no validity-checking of arguments.
C    -------
C
C  Fortran intrinsics used:  DABS, DMAX1, DMIN1.
C
C***END PROLOGUE  DPCHCI