c_csa3lxs - cubic spline approximation, expanded entry for
three-dimensional input, list output
float *c_csa3lxs(int, float [], float [], float [], float [],
float [], int [], float, int [],
int, float [], float [], float [], int *);
float *c_csa3lxs(int n, float xi[], float yi[], float zi[], float ui[],
float wts[], int knots[3], float smth, int nderiv[3],
int no, float xo[], float yo[], float zo[], int *ier);
- 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 dimensioned for n containing the Z coordinate
values for the input function.
- ui
- (real, input) An array containing the functional values of the input
function -- ui[k] is the functional value at (xi[k], yi[k], zi[k]) for
k=0,n-1.
- wts
- (real, input) An array containing weights for the ui values at the input
values, that is, wts[l] is a weight for the value of ui[l] for l=0,n-1. If
you do not desire to weight the input ui 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_csa3lxs 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], knots[1], and knots[2] 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
- (real, 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,
nderiv[1]=1 and nderiv[2]=0, then the second order mixed partial with
respect to X and Y would be computed.
- no
- (integer, input) The number of X - Y - Z 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.
- zo
- (real, output) An array dimensioned for no containing the Z 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.
c_csa3lxs is called to find values of an approximating cubic
spline at specified three-dimensional coordinates. c_csa3lxs 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_csa3ls.
c_csa3lxs 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_csa3lxs(n, x, y, z, u, wts, knots, smth, nderiv,
no, xo, yo, zo, &ier);
then out[i] is the approximated function value at coordinate point
(xo[i], yo[i], zo[i]) for 0 <= i < no. The space for out is allocated
internal to c_csa3lxs and is no floats in size.
To use c_csa3lxs, load the NCAR Graphics library ngmath.
csagrid, c_csa3s, c_csa3xs, c_csa3lxs
Complete documentation for Csagrid is available at URL
http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html
Copyright (C) 2000
University Corporation for Atmospheric Research
The use of this Software is governed by a License Agreement.