GRASS GIS 8 Programmer's Manual 8.2.1(2023)-exported
c_sep.c
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1/*!
2 \file cluster/c_sep.c
3
4 \brief Cluster library - Separation
5
6 (C) 2001-2009 by the GRASS Development Team
7
8 This program is free software under the GNU General Public License
9 (>=v2). Read the file COPYING that comes with GRASS for details.
10
11 \author Original author CERL
12*/
13
14#include <math.h>
15#include <grass/cluster.h>
16
17#define FAR ((double) -1.0)
18
19/*!
20 \brief ?
21
22 \param C pointer to Cluster structure
23 \param class1 1st class
24 \param class2 2nd class
25*/
26double I_cluster_separation(struct Cluster *C, int class1, int class2)
27{
28 int band;
29 double q;
30 double d;
31 double var;
32 double a1, a2;
33 double n1, n2;
34 double m1, m2;
35 double s1, s2;
36
37 if (C->count[class1] < 2)
38 return FAR;
39 if (C->count[class2] < 2)
40 return FAR;
41 n1 = (double)C->count[class1];
42 n2 = (double)C->count[class2];
43
44 d = 0.0;
45 a1 = a2 = 0.0;
46 for (band = 0; band < C->nbands; band++) {
47 s1 = C->sum[band][class1];
48 s2 = C->sum[band][class2];
49 m1 = s1 / n1;
50 m2 = s2 / n2;
51 q = m1 - m2;
52 q = q * q;
53 d += q;
54
55
56 var = C->sum2[band][class1] - (s1 * m1);
57 var /= n1 - 1;
58 if (var)
59 a1 += q / var;
60
61 var = C->sum2[band][class2] - (s2 * m2);
62 var /= n2 - 1;
63 if (var)
64 a2 += q / var;
65 }
66 if (d == 0.0)
67 return d;
68
69 if (a1 < 0 || a2 < 0)
70 return FAR;
71 if (a1)
72 a1 = sqrt(6 * d / a1);
73 if (a2)
74 a2 = sqrt(6 * d / a2);
75 q = a1 + a2;
76 if (q == 0.0)
77 return FAR;
78
79 return (sqrt(d) / q);
80}
#define FAR
Definition: c_sep.c:17
double I_cluster_separation(struct Cluster *C, int class1, int class2)
?
Definition: c_sep.c:26