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FITAP

       SUBROUTINE  FITAP (XNEW,YNEW,NPNEW, X,Y,NP, DELTA)
 C$    (Approximating Vectors)
 C$    This  routine  finds   a  reduced  set   of  points   which
 C$    approximate a curve defined by a set of points  (X(K),Y(K),
 C$    K=1,NP).  The accuracy of  the approximation is  controlled
 C$    by  specifying  the  maximum  deviation,  "DELTA",  allowed
 C$    between the  points  and the  approximating  vectors.   For
 C$    typical data, the number  of these vectors  is found to  be
 C$    inversely proportional to the  square root of DELTA.   This
 C$    routine may prove  useful in determining  a reduced set  of
 C$    points which  can satisfactorily  represent a  much  larger
 C$    set,  but  for  which  plotting  time  is  excessive.   The
 C$    arguments are:
 C$
 C$    XNEW(*).....New X values returned.
 C$    YNEW(*).....New Y values returned.
 C$    NPNEW.......Number of new (X,Y) pairs returned.  Space must
 C$                be available in XNEW(*) and YNEW(*) to store at
 C$                most NP items, since NPNEW .LE. NP on return.
 C$    X(*)........Old X values.
 C$    Y(*)........Old Y values.
 C$    NP..........Number of old (X,Y) values input.
 C$    DELTA.......Maximum deviation between the data points
 C$                and the required vector approximation (input).
 C$
 C$    Author: D.H. McLain, Algorithm  100, "Vector  Approximation
 C$            to Curves", Computer Journal 21, #2 (May 1978), pp.
 C$            178-180.
 C$    (04-MAR-82)