1c_cssgrid(3NCARG)                NCAR GRAPHICS               c_cssgrid(3NCARG)
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NAME

6       c_cssgrid - tension spline interpolation on a sphere
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FUNCTION PROTOTYPE

9       float *c_cssgrid(int, float [], float [], float [],
10                        int, int, float [], float [], int *);
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SYNOPSIS

14       float *c_cssgrid (n, rlat, rlon, f, ni, nj, plat, plon, ier)
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DESCRIPTION

18       n           The number of input data points, n > 2.
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20       rlat        An  array  containing  the  latitudes  of  the  input data,
21                   expressed in degrees.  The first three points must  not  be
22                   collinear (lie on a common great circle).
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24       rlon        An  array  containing  the  longitudes  of  the input data,
25                   expressed in degrees.
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27       f           Array containing data values. f[i] is the functional  value
28                   at (rlat[i],rlon[i]) for i = 0 to n-1.
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30       ni          The number of latitudes in the interpolated grid.
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32       nj          The  number of longitudes in the interpolated grid.  ni and
33                   nj can both be 1, allowing for interpolation  at  a  single
34                   point.
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36       plat        An  array  containing  the  latitudes  of  the points where
37                   interpolated values are to be computed.  The values in plat
38                   should be in degrees.
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40       plon        An  array of length nj containing the longitudes the output
41                   grid lines.  The values in plon should be in degrees.
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43       ier         An error return value. If *ier is returned as  0,  then  no
44                   errors  were  detected.  If *ier is non-zero, then refer to
45                   the error list in cssgrid_errors for details.
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USAGE

48       c_cssgrid is called to find an interpolating tension  spline  for  ran‐
49       domly positioned data on a unit sphere.
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RETURN VALUE

52       c_cssgrid  returns  a  pointer  to a linear array of data that contains
53       interpolated values at user-specified lat/lon pairs. The returned array
54       stores its values as if they were a 2-dimensional C array with latitude
55       being the first dimension and longitude the second dimension. That  is,
56       if out is declared as
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58         float *out;
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60       and we set:
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62         out = c_cssgrid(n, rlat, rlon, f, nlat, nlon, plat, plon, &ier);
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64       then  out[i*nlon+j]  is  the  interpolated function value at coordinate
65       point (plat[i], plon[j]) for 0 <= i < nlat and 0 <= j < nlon. The space
66       for out is allocated internal to c_cssgrid and is nlat * nlon floats in
67       size.
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ACCESS

70       To use c_cssgrid, load the NCAR Graphics library ngmath.
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SEE ALSO

73       css_overview, cssgrid_errors
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75       Complete documentation for Cssgrid is available at URL
76       http://ngwww.ucar.edu/ngdoc/ng/ngmath/cssgrid/csshome.html
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79       Copyright (C) 2000
80       University Corporation for Atmospheric Research
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82       This documentation is free software; you  can  redistribute  it  and/or
83       modify  it  under  the  terms of the GNU General Public License as pub‐
84       lished by the  Free  Software  Foundation;  either  version  2  of  the
85       License, or (at your option) any later version.
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87       This  software  is  distributed in the hope that it will be useful, but
88       WITHOUT ANY  WARRANTY;  without  even  the  implied  warranty  of  MER‐
89       CHANTABILITY  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
90       Public License for more details.
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92       You should have received a copy of the GNU General Public License along
93       with  this  software;  if  not,  write to the Free Software Foundation,
94       Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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99UNIX                               May 2000                  c_cssgrid(3NCARG)
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