Provided by: libncarg-dev_6.4.0-9_amd64 bug

NAME

       c_ftcurvs1 - calculate values for a smoothing spline for data in the plane.

FUNCTION PROTOTYPE

       int c_ftcurvs1(int, float [], float [], int, float [],
                      int, float, float, float [], float []);

SYNOPSIS

       int c_ftcurvs1(int n, float xi[], float yi[], int dflg,
                      float d[], int m, float xl, float xr,
                      float xo[], float yo[])

DESCRIPTION

       n           The number of input data points. (n > 1)

       xi          An  array  containing the X-coordinates for the input data.  These need not be
                   increasing.

       yi          An array containing the Y-coordinates for the input data.

       dflg        A switch for interpreting the value of d (as  described  below).   If  dflg=0,
                   then  d is an array of length n (an error estimate for each input data value);
                   if dflg=1, then d is a scalar that serves  as  an  error  estimate  for  every
                   single data item.

       d           A  user-specified  value  containing  the observed weights. D may be either an
                   array or a scalar, depending on the value of dflg.

       m           The number of output values.

       xl          A lower limit for an interval of interpolation.  The interval between zero and
                   one  interpolates  the  entire  curve, any value outside this range results in
                   extrapolation.  The interval [xl,xr] is divided into m equal values to produce
                   the interpolated curve.

       xr          An  upper  limit  for an interval of interpolation.  The interval between zero
                   and one interpolates the entire curve, any value outside this range results in
                   extrapolation.  The interval [xl,xr] is divided into m equal values to produce
                   the interpolated curve.

       xo          The interpolated X values.

       yo          The interpolated Y values.

RETURN VALUE

       c_ftcurvs1 returns an error value as per:

       = 1 if n is less than 2.
       = 2 if smt is negative.
       = 3 if eps is negative or greater than 1.
       = 5 if d is negative.

USAGE

       This function computes an interpolatory smoothing spline under tension through a  sequence
       of data values in the plane.

       Two  parameters  and one function argument are used to control the degree of smoothness --
       the parameters are smt, and eps and the function argument is d.

       The argument d is a value indicating the degree of confidence in the accuracy of the input
       function  values  --  it  should  be  an approximation of the standard deviation of error.
       Effectively the value of d controls how close the smoothed curve comes to the  input  data
       points.  If d is small, then the interpolated curve will pass close to the input data. The
       larger the value of d, the more freedom the smooth curve has in how close it comes to  the
       input data values.

       The  parameter  smt is a more subtle global smoothing parameter; smt must be non-negative.
       For small values of smt, the curve approximates the tension spline and for  larger  values
       of  smt,  the  curve  is smoother. A reasonable value for smt is (float) n. smt can be set
       with the procedure c_ftsetr.

       The parameter eps controls the precision to which smt is interpreted; eps must be  between
       0.  and 1. inclusive. A reasonable value for eps sqrt( 2./(float) n ). eps can be set with
       the procedure c_ftsetr.

       c_ftcurvs1 is called after all of the desired values for control parameters have been  set
       using  the  procedures  c_ftseti,  c_ftsetr,  c_ftsetc.  Control  parameters that apply to
       c_ftcurvs are: sig, smt, eps, sf2.

       The value for the parameter sig specifies the tension factor.  Values near zero result  in
       a  cubic spline; large values (e.g. 50) result in nearly a polygonal line. A typical value
       is 1. (the default).

ACCESS

       To use c_ftcurvs1, load the NCAR Graphics library ngmath.

SEE ALSO

       fitgrid_params, c_ftseti, c_ftsetr, c_ftsetc.

       Complete documentation for Fitgrid is available at URL
       http://ngwww.ucar.edu/ngdoc/ng/ngmath/fitgrid/fithome.html

COPYRIGHT

       Copyright (C) 2000
       University Corporation for Atmospheric Research

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