NAME

c_csa2s - cubic spline approximation, simple entry for two-dimensional input, gridded output

FUNCTION PROTOTYPE

float *c_csa2s(int, float [], float [], float [], int [],


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

SYNOPSIS

int c_csa2s(int n, float xi[], float yi[], float zi[], int knots[2],


            int no, int mo, 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.

knots

(integer, input) The number of knots to be used in each coordinate direction 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.

no

(integer, input) The number of X coordinate values to be calculated for the output surface.

mo

(integer, input) The number of Y coordinate values to be calculated for the output surface.

xo

(real, input) An array dimensioned for no containing the X coordinates of the output grid.

yo

(real, output) An array dimensioned for mo containing the Y coordinates of the output grid.

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_csa2s is called to find an approximating cubic spline surface for two-dimensional input data. If you want to weight the input data values, calculate derivatives, or handle data sparse areas specially, then you will need to use c_csa2xs.

c_csa2s returns a pointer to a linear array of data that is the approximated grid stored in row-major order. That is, if out is declared as

  float *out;

and we set:

  out = c_csa2s(n, x, y, z, knots, no, mo, xo, yo, &ier);

then out[i*mo+j] is the approximated function value at coordinate point (xo[i], yo[j]) for 0 <= i < no and 0 <= j < mo. The space for out is allocated internal to c_csa2s and is no * mo floats in size.

ACCESS

To use c_csa2s, load the NCAR Graphics library ngmath.

SEE ALSO

csagrid, c_csa2xs, c_csa2ls, c_csa2lxs

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.