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SUBROUTINE DATSM

PURPOSE
   NDIM POINTS OF A GIVEN TABLE WITH MONOTONIC ARGUMENTS ARE
   SELECTED AND ORDERED SUCH THAT
   ABS(ARG(I)-X).GE.ABS(ARG(J)-X) IF I.GT.J.

USAGE
   CALL DATSM (X,Z,F,IROW,ICOL,ARG,VAL,NDIM)

DESCRIPTION OF PARAMETERS
   X	  - DOUBLE PRECISION SEARCH ARGUMENT.
   Z	  - DOUBLE PRECISION VECTOR OF ARGUMENT VALUES (DIMEN-
	    SION IROW). THE ARGUMENT VALUES MUST BE STORED IN
	    INCREASING OR DECREASING SEQUENCE.
   F	  - IN CASE ICOL=1, F IS THE DOUBLE PRECISION VECTOR
	    OF FUNCTION VALUES (DIMENSION IROW).
	    IN CASE ICOL=2, F IS A DOUBLE PRECISION IROW BY 2
	    MATRIX. THE FIRST COLUMN SPECIFIES VECTOR OF FUNC-
	   TION VALUES AND THE SECOND VECTOR OF DERIVATIVES.
   IROW   - THE DIMENSION OF VECTOR Z AND OF EACH COLUMN
	    IN MATRIX F.
   ICOL   - THE NUMBER OF COLUMNS IN F (I.E. 1 OR 2).
   ARG	  - RESULTING DOUBLE PRECISION VECTOR OF SELECTED AND
	    ORDERED ARGUMENT VALUES (DIMENSION NDIM).
   VAL	  - RESULTING DOUBLE PRECISION VECTOR OF SELECTED
	    FUNCTION VALUES (DIMENSION NDIM) IN CASE ICOL=1.
	    IN CASE ICOL=2, VAL IS THE DOUBLE PRECISION VECTOR
	    OF FUNCTION AND DERIVATIVE VALUES (DIMENSION
	    2*NDIM) WHICH ARE STORED IN PAIRS (I.E. EACH FUNC-
	    TION VALUE IS FOLLOWED BY ITS DERIVATIVE VALUE).
   NDIM   - THE NUMBER OF POINTS WHICH MUST BE SELECTED OUT OF
	    THE GIVEN TABLE (Z,F).

REMARKS
   NO ACTION IN CASE IROW LESS THAN 1.
   IF INPUT VALUE NDIM IS GREATER THAN IROW, THE PROGRAM
   SELECTS ONLY A MAXIMUM TABLE OF IROW POINTS.  THEREFORE THE
   USER OUGHT TO CHECK CORRESPONDENCE BETWEEN TABLE (ARG,VAL)
   AND ITS DIMENSION BY COMPARISON OF NDIM AND IROW, IN ORDER
   TO GET CORRECT RESULTS IN FURTHER WORK WITH TABLE (ARG,VAL).
   THIS TEST MAY BE DONE BEFORE OR AFTER CALLING
   SUBROUTINE DATSM.
   SUBROUTINE DATSM ESPECIALLY CAN BE USED FOR GENERATING THE
   TABLE (ARG,VAL) NEEDED IN SUBROUTINES DALI, DAHI, AND DACFI.

SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
   NONE

METHOD
   SELECTION IS DONE BY SEARCHING THE SUBSCRIPT J OF THAT
   ARGUMENT, WHICH IS NEXT TO X (BINARY SEARCH).
   AFTERWARDS NEIGHBOURING ARGUMENT VALUES ARE TESTED AND
   SELECTED IN THE ABOVE SENSE.