ncl_c_csa2s man page

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

Info

January 1999 UNIX NCAR GRAPHICS