GRASS GIS 8 Programmer's Manual 8.2.0(2022)-exported
watsonue.c
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1#include <stdio.h>
2#include <stdlib.h>
3#include <math.h>
4#include "local_proto.h"
5
6
7double *Cdhc_watson_u2_exp(double *x, int n)
8{
9 double *xcopy, mean = 0.0, zbar = 0.0, fn2, fx, sum4 = 0.0;
10 static double y[2];
11 int i;
12
13 if ((xcopy = (double *)malloc(n * sizeof(double))) == NULL) {
14 fprintf(stderr, "Memory error in Cdhc_watson_u2_exp\n");
15 exit(EXIT_FAILURE);
16 }
17
18 for (i = 0; i < n; ++i) {
19 xcopy[i] = x[i];
20 mean += x[i];
21 }
22 mean /= n;
23
24 qsort(xcopy, n, sizeof(double), Cdhc_dcmp);
25
26 for (i = 0; i < n; ++i) {
27 fx = 1 - exp(-xcopy[i] / mean);
28 if (fx <= 1e-5)
29 fx = 1e-5;
30
31 if (fx >= 0.99999)
32 fx = 0.99999;
33
34 /* sum3 += 2 * (i + 1) * (log (fx) + log (1.0 - fx[n - i - 1])); */
35 fn2 = (2.0 * i + 1.0) / (2.0 * n);
36 sum4 += (fx - fn2) * (fx - fn2);
37 fn2 = (2.0 * (i + 1) - 1.0) / (2.0 * n);
38 zbar += fx;
39 }
40
41 zbar /= n;
42 y[0] = (1.0 / (n * 12) + sum4) - n * (zbar - .5) * (zbar - .5);
43 y[0] *= 1.0 + 0.16 / n;
44
45#ifdef NOISY
46 fprintf(stdout, " TEST19 WU2(E) =%10.4f\n", y[0]);
47#endif /* NOISY */
48
49 free(xcopy);
50
51 return y;
52}
#define NULL
Definition: ccmath.h:32
int Cdhc_dcmp(const void *i, const void *j)
Definition: dcmp.c:1
double * Cdhc_watson_u2_exp(double *x, int n)
Definition: watsonue.c:7
#define x