Provided by: libncarg-dev_6.4.0-9_amd64 
NAME
c_csa2lxs - cubic spline approximation, expanded entry for two-dimensional input, list
output
FUNCTION PROTOTYPE
float *c_csa2lxs(int, float [], float [], float [], float [], int [],
float, int [], int, float [], float [], int *);
SYNOPSIS
int c_csa2lxs(int n, float xi[], float yi[], float zi[],
float wts[], int knots[2], float smth, int nderiv[2],
int no, float xo[], float yo[], 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 X coordinate values
for the input function.
yi (real, input) An array dimensioned for n containing the Y coordinate values
for the input function.
zi (real, input) An array containing the functional values of the input function
-- zi[k] is the functional value at (xi[k], yi[k]) for k=0,n-1.
wts (real, input) An array containing weights for the zi values at the input xi
and yi values, that is, wts[l] is a weight for the value of zi[l] for l=0,n-1.
If you do not desire to weight the input zi 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_csa2lxs 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[0] and knots[1] 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) For each of the two coordinate direction, specifies whether
you want functional values (nderiv=0), first derivative values (nderiv=1), or
second derivative values (nderiv=2). For example, if nderiv[0]=1 and
nderiv[1]=1, then the second order mixed partial would be computed.
no (integer, input) The number of X - Y coordinate values to be calculated for
the output array.
xo (real, input) An array dimensioned for no containing the X coordinates of the
output list.
yo (real, output) An array dimensioned for no containing the Y coordinates of the
output list.
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_csa2lxs is called to find values of an approximating cubic spline at specified two-
dimensional coordinates. If you want to weight the input data values, calculate
derivatives, or handle data sparse areas specially, then you will need to use c_csa2lxs.
c_csa2lxs returns a pointer to a linear array of data that contains the approximated
values calculated at the input list of coordinate values. That is, if out is declared as
float *out;
and we set:
out = c_csa2lxs(n, x, y, z, wts, knots, smth, nderiv, no, xo, yo, &ier);
then out[i] is the approximated function value at coordinate point (xo[i], yo[i]) for 0 <=
i < no. The space for out is allocated internal to c_csa2lxs and is no floats in size.
ACCESS
To use c_csa2lxs, load the NCAR Graphics library ngmath.
SEE ALSO
csagrid, c_csa2s, c_csa2xs, c_csa2ls
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.