C
C     ..................................................................
C
C        SUBROUTINE DSE13
C
C        PURPOSE
C           TO COMPUTE A VECTOR OF SMOOTHED FUNCTION VALUES GIVEN A
C           VECTOR OF FUNCTION VALUES WHOSE ENTRIES CORRESPOND TO
C           EQUIDISTANTLY SPACED ARGUMENT VALUES.
C
C        USAGE
C           CALL DSE13(Y,Z,NDIM,IER)
C
C        DESCRIPTION OF PARAMETERS
C           Y     -  GIVEN VECTOR OF DOUBLE PRECISION FUNCTION VALUES
C                    (DIMENSION NDIM)
C           Z     -  RESULTING VECTOR OF DOUBLE PRECISION SMOOTHED
C                    FUNCTION VALUES (DIMENSION NDIM)
C           NDIM  -  DIMENSION OF VECTORS Y AND Z
C           IER   -  RESULTING ERROR PARAMETER
C                    IER = -1  - NDIM IS LESS THAN 3
C                    IER =  0  - NO ERROR
C
C        REMARKS
C           (1)  IF IER=-1 THERE HAS BEEN NO COMPUTATION.
C           (2)   Z CAN HAVE THE SAME STORAGE ALLOCATION AS Y.  IF Y
C                 IS DISTINCT FROM Z, THEN IT IS NOT DESTROYED.
C
C        SUBROUTINES AND SUBPROGRAMS REQUIRED
C           NONE
C
C        METHOD
C           IF X IS THE (SUPPRESSED) VECTOR OF ARGUMENT VALUES, THEN
C           EXCEPT AT THE ENDPOINTS X(1) AND X(NDIM), EACH SMOOTHED
C           VALUE Z(I) IS OBTAINED BY EVALUATING AT X(I) THE LEAST-
C           SQUARES POLYNOMIAL OF DEGREE 1 RELEVANT TO THE 3 SUCCESSIVE
C           POINTS (X(I+K),Y(I+K)) K = -1,0,1.  (SEE HILDEBRAND, F.B.,
C           INTRODUCTION TO NUMERICAL ANALYSIS, MC GRAW-HILL, NEW YORK/
C           TORONTO/LONDON, 1956, PP. 295-302.)
C
C     ..................................................................
C
      SUBROUTINE DSE13(Y,Z,NDIM,IER)
C
      DIMENSION Y(1),Z(1)
      DOUBLE PRECISION Y,Z,A,B,C
C
C        TEST OF DIMENSION
      IF(NDIM-3)3,1,1
C
C        PREPARE LOOP
    1 B=.16666666666666667D0*(5.D0*Y(1)+Y(2)+Y(2)-Y(3))
      C=.16666666666666667*(5.D0*Y(NDIM)+Y(NDIM-1)+Y(NDIM-1)-Y(NDIM-2))
C
C        START LOOP
      DO 2 I=3,NDIM
      A=B
      B=.33333333333333333D0*(Y(I-2)+Y(I-1)+Y(I))
    2 Z(I-2)=A
C        END OF LOOP
C
C        UPDATE LAST TWO COMPONENTS
      Z(NDIM-1)=B
      Z(NDIM)=C
      IER=0
      RETURN
C
C        ERROR EXIT IN CASE NDIM IS LESS THAN 3
    3 IER=-1
      RETURN
      END