grass-addons/src/imagery/i.pr/PRLIB/bootstrap.c at d7657409b0a39b9af9105a7fae6512a57755cc22 · OSGeo/grass-addons · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
/*
   The following routines are written and tested by Stefano Merler

   for

   bootstrap, probabily based, samples estraction
 */

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <grass/gis.h>
#include "global.h"

void Bootsamples(int n, double *prob, int *random_labels)

/*
   given an array of probabilities of length n, extract a bootstrap sample
   of n elements according to the vector of probabilities
 */
{
    int i, j;
    int *random_labels_flag;
    double *random;
    double *cumprob;
    double probtot = .0;

    for (i = 0; i < n; i++)
        probtot += prob[i];
    for (i = 0; i < n; i++)
        prob[i] /= probtot;

    random_labels_flag = (int *)G_calloc(n, sizeof(int));
    random = (double *)G_calloc(n, sizeof(double));
    cumprob = (double *)G_calloc(n, sizeof(double));

    for (i = 0; i < n; ++i) {
        random[i] = G_drand48();
        random_labels[i] = n - 1;
        random_labels_flag[i] = 0;
    }

    for (i = 0; i < n; i++) {
        if (i > 0)
            cumprob[i] = cumprob[i - 1] + prob[i];
        else
            cumprob[0] = prob[0];

        for (j = 0; j < n; j++) {

            if (random[j] < cumprob[i])
                if (random_labels_flag[j] == 0) {
                    random_labels[j] = i;
                    random_labels_flag[j] = 1;
                }
        }
    }

    G_free(random);
    G_free(cumprob);
    G_free(random_labels_flag);
}

void Bootsamples_rseed(int n, double *prob, int *random_labels, int *idum)
/*
   given an array of probabilities of length n, extract a bootstrap sample
   of n elements according to the vector of probabilities
 */
{
    int i, j;
    int *random_labels_flag;
    double *random;
    double *cumprob;
    double probtot = .0;

    for (i = 0; i < n; i++)
        probtot += prob[i];
    for (i = 0; i < n; i++)
        prob[i] /= probtot;

    random_labels_flag = (int *)G_calloc(n, sizeof(int));
    random = (double *)G_calloc(n, sizeof(double));
    cumprob = (double *)G_calloc(n, sizeof(double));

    for (i = 0; i < n; ++i) {
        random[i] = (double)ran1(idum);
        random_labels[i] = n - 1;
        random_labels_flag[i] = 0;
    }

    for (i = 0; i < n; i++) {
        if (i > 0)
            cumprob[i] = cumprob[i - 1] + prob[i];
        else
            cumprob[0] = prob[0];

        for (j = 0; j < n; j++) {

            if (random[j] < cumprob[i])
                if (random_labels_flag[j] == 0) {
                    random_labels[j] = i;
                    random_labels_flag[j] = 1;
                }
        }
    }

    G_free(random);
    G_free(cumprob);
    G_free(random_labels_flag);
}