1c_csvoro(3NCARG) NCAR GRAPHICS c_csvoro(3NCARG)
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6 c_csvoro - calculate Voronoi polygons for points on a sphere.
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9 void c_csvoro(int, float [], float [],
10 int, int, float [], float [], float [],
11 int *, int *, int [], int *);
12
15 void *c_csvoro (n, rlat, rlon, ni, nf, plat, plon, rc,
16 nca, numv, nv, ier);
17
20 n The number of input data points, n > 2.
21 rlat An array containing the latitudes of the input data,
23 expressed in degrees. The first three points must not be
24 collinear (lie on a common great circle).
25 rlon An array containing the longitudes of the input data,
27 expressed in degrees.
28 ni The index of the input coordinate for which you want to
30 determine the Voronoi polygon (0 <= ni < n).
31 nf Flag indicating if this is the first call to c_csvoro to
33 retrieve Voronoi polygons for this dataset (1=yes, 0=no).
34 Calls subsequent to the first call for a given dataset are
35 much faster than the first call.
36 plat The latitudes for the vertices of the Voronoi polygons.
38 These are circumcenters of circles passing through the
39 Delaunay triangles. If a coordinate is a boundary point,
40 then the circle may pass through certain "pseudo points"
41 that have been added to the original dataset in order to
42 complete the Voronoi polygon.
43 plon The longitudes for the vertices of the Voronoi polygons.
45 rc Array containing circumradii (arc lengths in degrees of the
47 angle between a circumcenter and its associated triangle
48 vertices).
49 nca *nca is the actual number of circumcenters returned in plat
51 and plon. This number may be larger than n if the input
52 dataset has boundary points, since certain "pseudo points"
53 may have been added to the original dataset in order to
54 complete the Voronoi polygon set.
55 numv *numv is the number of vertices in the Voronoi polygon
57 enclosing the coordinate (rlat[ni],rlon[ni]).
58 nv An array containing numv indices for the Voronoi polygon
60 enclosing the coordinate (rlat[ni],rlon[ni]). The indices
61 returned in this array refer to the coordinates returned in
62 plat and plon. For example, if the integer "j" is an ele‐
63 ment of the nv array, then (plat[j],plon[j]) is a vertex of
64 the Voronoi polygon enclosing (rlat[ni],rlon[ni]). The
65 indices in nv list out the vertices of the Voronoi polygon
66 in counter-clockwise order.
67 ier An error return value. If *ier is returned as 0, then no
69 errors were detected. If *ier is non-zero, then refer to
70 the error list in the error table for details.
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73 c_csvoro is called if you want to determine the Voronoi polygons for
74 data randomly positioned on a sphere. Each call to c_csvoro calculates
75 the vertices for the Voronoi polygon surrounding a specified input
76 point.
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79 To use c_csvoro, load the NCAR Graphics library ngmath.
80
82 css_overview, c_cssgrid, cssgrid_errors
83 Complete documentation for Cssgrid is available at URL
85 http://ngwww.ucar.edu/ngdoc/ng/ngmath/cssgrid/csshome.html
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88 Copyright (C) 2000
89 University Corporation for Atmospheric Research
90 The use of this Software is governed by a License Agreement.
92UNIX May 2000 c_csvoro(3NCARG)