Provided by: libncarg-dev_6.3.0-6build1_amd64

**NAME**

c_csa3ls - cubic spline approximation, simple entry for three-dimensional input, list output

**FUNCTION** **PROTOTYPE**

float *c_csa3ls(int, float [], float [], float [], float [], int [], int, float [], float [], float[], int *);

**SYNOPSIS**

float *c_csa3ls(int n, float xi[], float yi[], float zi[], float ui[], int knots[3], int no, float xo[], float yo[], float zo[], int *);

**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 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. 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. 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. 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.

**USAGE**

c_csa3ls is called to find values of an approximating cubic spline at specified three- 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_csa3lxs. c_csa3ls 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_csa3ls(n, x, y, z, u, knots, 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_csa3ls and is no floats in size.

**ACCESS**

To use c_csa3ls, load the NCAR Graphics library ngmath.

**SEE** **ALSO**

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**

Copyright (C) 2000 University Corporation for Atmospheric Research The use of this Software is governed by a License Agreement.