NAME

       c_csa1xs - cubic spline approximation, expanded entry for one-dimensional input

FUNCTION PROTOTYPE

       float *c_csa1xs(int, float [], float [], float [], int,
                    float, int, int, float [], int *);

SYNOPSIS

       float *c_csa1xs(int n, float xi[], float yi[], float wts[],
                       int knots, float smth, int nderiv,
                       int m, float xo[], int *ier);

DESCRIPTION

       n           (integer,input)  The  number  of  input data points. It must be that n is greater than 3 and,
                   depending on the size of knots below, n may have to be larger.

       xi          (real, input) An array dimensioned for n containing the abscissae for the input function.

       yi          (real, input) An array dimensioned for n  containing  the  functional  values  of  the  input
                   function -- yi[k] is the functional value at xi[k] for k=0,n-1.

       wts         (real, input) An array dimensioned for n containing weights for the yi values at the input xi
                   values, that is, wts[l] is a weight for the value of yi[l] for l=0,n-1. If you do not  desire
                   to  weight  the  input  yi  values,  then  set wts[0] to -1. The weights in the wts array are
                   relative and may be set to any non-negative value.  When c_csa1xs is called, the weights  are
                   summed and the individual weights are normalized so that the weight sum is unity.

       knots       (integer,  input)  The  number  of knots to be used in constructing the approximation spline.
                   knots must be at least 4. The larger the value for knots, the closer the  approximated  curve
                   will come to passing through the input function values.

       smth        (real,  input)  A parameter that controls extrapolation into data sparse regions.  If smth is
                   zero, then nothing special is done in data sparse regions.  A good first choice for  smth  is
                   1.

       nderiv      (integer,  input)  Specifies  whether you want functional values (nderiv=0), first derivative
                   values (nderiv=1), or second derivative values (nderiv=2).

       m           (integer, input) The number of values to be calculated for the output curve.

       xo          (real, input) An array dimensioned for m containing the X coordinates of the output curve.

       ier         (pointer to integer, output) An error return value. If *ier is returned as 0, then no  errors
                   were  detected.  If  *ier  is  non-zero,  then refer to the error list in the error table for
                   details.

USAGE

       c_csa1xs is called to find an approximating cubic spline for one-dimensional  input  data.   c_csa1xs  is
       called  if  you  want to weight the input data values, calculate derivatives, or handle data sparse areas
       specially.  If you do not want to do any of these three things, then use c_csa1s.

       c_csa1s returns a pointer to a linear array of data that is the approximated curve.

ACCESS

       To use c_csa1xs, load the NCAR Graphics library ngmath.

SEE ALSO

       csagrid, c_csa1s, c_csa1ls, c_csa1lxs

       Complete documentation for Csagrid is available at URL
       http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html

COPYRIGHT

       Copyright (C) 2000
       University Corporation for Atmospheric Research

       The use of this Software is governed by a License Agreement.