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SUBROUTINE SE13

PURPOSE
   TO COMPUTE A VECTOR OF SMOOTHED FUNCTION VALUES GIVEN A
   VECTOR OF FUNCTION VALUES WHOSE ENTRIES CORRESPOND TO
   EQUIDISTANTLY SPACED ARGUMENT VALUES.

USAGE
   CALL SE13(Y,Z,NDIM,IER)

DESCRIPTION OF PARAMETERS
   Y	 -  GIVEN VECTOR OF FUNCTION VALUES (DIMENSION NDIM)
   Z	 -  RESULTING VECTOR OF SMOOTHED FUNCTION VALUES
	    (DIMENSION NDIM)
   NDIM  -  DIMENSION OF VECTORS Y AND Z
   IER	 -  RESULTING ERROR PARAMETER
	    IER = -1  - NDIM IS LESS THAN 3
	    IER =  0  - NO ERROR

REMARKS
   (1)	IF IER=-1 THERE HAS BEEN NO COMPUTATION.
   (2)	 Z CAN HAVE THE SAME STORAGE ALLOCATION AS Y.  IF Y
	 IS DISTINCT FROM Z, THEN IT IS NOT DESTROYED.

SUBROUTINES AND SUBPROGRAMS REQUIRED
   NONE

METHOD
   IF X IS THE (SUPPRESSED) VECTOR OF ARGUMENT VALUES, THEN
   EXCEPT AT THE ENDPOINTS X(1) AND X(NDIM), EACH SMOOTHED
   VALUE Z(I) IS OBTAINED BY EVALUATING AT X(I) THE LEAST-
   SQUARES POLYNOMIAL OF DEGREE 1 RELEVANT TO THE 3 SUCCESSIVE
   POINTS (X(I+K),Y(I+K)) K = -1,0,1.  (SEE HILDEBRAND, F.B.,
   INTRODUCTION TO NUMERICAL ANALYSIS, MC GRAW-HILL, NEW YORK/
   TORONTO/LONDON, 1956, PP. 295-302.)