GRASS Programmer's Manual  6.5.svn(2014)-r66266
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c_kurt.c
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1 #include <grass/gis.h>
2 
3 void c_kurt(DCELL * result, DCELL * values, int n, const void *closure)
4 {
5  DCELL sum, ave, sumsq, sumqt, var;
6  int count;
7  int i;
8 
9  sum = 0.0;
10  count = 0;
11 
12  for (i = 0; i < n; i++) {
13  if (G_is_d_null_value(&values[i]))
14  continue;
15 
16  sum += values[i];
17  count++;
18  }
19 
20  if (count == 0) {
21  G_set_d_null_value(result, 1);
22  return;
23  }
24 
25  ave = sum / count;
26 
27  sumsq = 0;
28 
29  for (i = 0; i < n; i++) {
30  DCELL d;
31 
32  if (G_is_d_null_value(&values[i]))
33  continue;
34 
35  d = values[i] - ave;
36  sumsq += d * d;
37  sumqt += d * d * d * d;
38  }
39 
40  var = sumsq / count;
41 
42  *result = sumqt / (count * var * var) - 3;
43 }
44 
45 void w_kurt(DCELL * result, DCELL(*values)[2], int n, const void *closure)
46 {
47  DCELL sum, ave, sumsq, sumqt, var;
48  int count;
49  int i;
50 
51  sum = 0.0;
52  count = 0;
53 
54  for (i = 0; i < n; i++) {
55  if (G_is_d_null_value(&values[i][0]))
56  continue;
57 
58  sum += values[i][0] * values[i][1];
59  count += values[i][1];
60  }
61 
62  if (count == 0) {
63  G_set_d_null_value(result, 1);
64  return;
65  }
66 
67  ave = sum / count;
68 
69  sumsq = 0;
70 
71  for (i = 0; i < n; i++) {
72  DCELL d;
73 
74  if (G_is_d_null_value(&values[i][0]))
75  continue;
76 
77  d = values[i][0] - ave;
78  sumsq += d * d * values[i][1];
79  sumqt += d * d * d * values[i][1];
80  }
81 
82  var = sumsq / count;
83 
84  *result = sumqt / (count * var * var) - 3;
85 }
G_set_d_null_value
void G_set_d_null_value(DCELL *dcellVals, int numVals)
Definition: null_val.c:176
count
int count
G_is_d_null_value
int G_is_d_null_value(const DCELL *dcellVal)
Returns 1 if dcell is NULL, 0 otherwise. This will test if the value dcell is a NaN. Same test as in G_is_f_null_value().
Definition: null_val.c:306
w_kurt
void w_kurt(DCELL *result, DCELL(*values)[2], int n, const void *closure)
Definition: c_kurt.c:45
c_kurt
void c_kurt(DCELL *result, DCELL *values, int n, const void *closure)
Definition: c_kurt.c:3
n
int n
Definition: dataquad.c:291