Provided by: libncarg-dev_6.1.2-7_amd64 
NAME
c_ftsurf - 2D tension spline interpolation of rectangular data
FUNCTION PROTOTYPE
float *c_ftsurf (int, int, float *, float *, float *,
int, int, float *, float *, int *);
SYNOPSIS
float *c_ftsurf (mi, ni, xi, yi, zi, mo, no, xo, yo, ier);
DESCRIPTION
mi The number of grid lines in the X direction. (mi > 1)
ni The number of grid lines in the Y direction. (ni > 1)
xi Pointer to an array containing m X coordinates for grid lines in the X
direction.
yi Pointer to an array containing n Y coordinates for grid lines in the Y
direction.
zi Pointer to m x n floats which are the functional values at the grid points
defined by xi and yi.
mo The number of output values in the X direction.
no The number of output values in the Y direction.
ier The value *ier is an error flag as per:
= 0 -- no error.
= 1 -- if n is less than 2 or m is less than 2.
= 2 -- if X or Y values are not strictly increasing.
RETURN VALUE
c_ftsurf returns a pointer to an array containing mo x no floats which are the
interpolated values on the grid specified by the arrays xo and yo.
USAGE
This procedure calculates an interpolatory surface passing through a rectangular grid of
function values. The surface computed is a tensor product of splines under tension.
c_ftsurf is called after all of the desired values for control parameters have been set
using the procedures c_ftseti, c_ftsetr, c_ftsetc, c_ftsetfa. The control parameters that
apply to c_ftsurf are: sig, zx1, zxm, zy1, zyn, z11, zm1, z1n, zmn, df1, df2, df3, df4,
df5, df6, df7, df8
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).
zx1 is an array containing n X-partial derivatives of the function along the line xi[0],
that is zx1[j] is the X-partial derivative at point (x[0],y[j]) for j=0,n-1. This
parameter may be defaulted by setting the value for df1 appropriately. The default is to
compute zx1 internally. Values for zx1 can be set using the procedure c_ftsetfa.
zxm is an array containing n X-partial derivatives of the function along the line xi[m-1],
that is zxm[j] is the X-partial derivative at point (xi[m-1],yi[j]) for j=0,n-1. This
parameter may be defaulted by setting the value for df2 appropriately. The default is to
compute zx2 internally. Values for zxm can be set using the procedure c_ftsetfa.
zy1 is an array containing m Y-partial derivatives of the function along the line yi[0],
that is zy1[j] is the Y-partial derivative at point (x[i],y[0]) for i=0,m-1. This
parameter may be defaulted by setting the value for df3 appropriately. The default is to
compute zy1 internally. Values for zy1 can be set using the procedure c_ftsetfa.
zyn is an array containing m Y-partial derivatives of the function along the line yi[n-1],
that is zyn[j] is the Y-partial derivative at point (x[i],y[n-1]) for i=0,m-1. This
parameter may be defaulted by setting the value for df4 appropriately. The default is to
compute zyn internally. Values for zyn can be set using the procedure c_ftsetfa.
z11, zm1, z1n, zmn specify X-Y-partial derivatives of the function at the four corners
(xi[0],yi[0]), (xi[m-1],yi[0]), (xi[0],yi[n-1]), (xi[m-1],yi[n-1]), These parameters may
be defaulted by setting the values for df5, df6, df7, df8, appropriately. The default is
to compute z11, zm1, z1n, zmn internally.
ACCESS
To use c_ftsurf, 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.