GRASS GIS 8 Programmer's Manual 8.4.1(2025)-45ca3179ab
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c_var.c
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1#include <grass/gis.h>
2#include <grass/raster.h>
3
4void c_var(DCELL *result, DCELL *values, int n, const void *closure UNUSED)
5{
6 DCELL sum, ave, sumsq;
7 int count;
8 int i;
9
10 sum = 0.0;
11 count = 0;
12
13 for (i = 0; i < n; i++) {
14 if (Rast_is_d_null_value(&values[i]))
15 continue;
16
17 sum += values[i];
18 count++;
19 }
20
21 if (count == 0) {
22 Rast_set_d_null_value(result, 1);
23 return;
24 }
25
26 ave = sum / count;
27
28 sumsq = 0;
29
30 for (i = 0; i < n; i++) {
31 DCELL d;
32
33 if (Rast_is_d_null_value(&values[i]))
34 continue;
35
36 d = values[i] - ave;
37 sumsq += d * d;
38 }
39
40 *result = sumsq / count;
41}
42
43void w_var(DCELL *result, DCELL (*values)[2], int n, const void *closure UNUSED)
44{
45 DCELL sum, ave, sumsq;
46 DCELL count;
47 int i;
48
49 sum = 0.0;
50 count = 0;
51
52 for (i = 0; i < n; i++) {
53 if (Rast_is_d_null_value(&values[i][0]))
54 continue;
55
56 sum += values[i][0] * values[i][1];
57 count += values[i][1];
58 }
59
60 if (count == 0) {
61 Rast_set_d_null_value(result, 1);
62 return;
63 }
64
65 ave = sum / count;
66
67 sumsq = 0;
68
69 for (i = 0; i < n; i++) {
70 DCELL d;
71
72 if (Rast_is_d_null_value(&values[i][0]))
73 continue;
74
75 d = values[i][0] - ave;
76 sumsq += d * d * values[i][1];
77 }
78
79 *result = sumsq / count;
80}
void c_var(DCELL *result, DCELL *values, int n, const void *closure UNUSED)
Definition c_var.c:4
void w_var(DCELL *result, DCELL(*values)[2], int n, const void *closure UNUSED)
Definition c_var.c:43
int count