GRASS GIS 8 Programmer's Manual  8.4.0dev(2024)-2653d7b383
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 double *Cdhc_watson_u2_exp(double *x, int n)
7 {
8  double *xcopy, mean = 0.0, zbar = 0.0, fn2, fx, sum4 = 0.0;
9  static double y[2];
10  int i;
11 
12  if ((xcopy = (double *)malloc(n * sizeof(double))) == NULL) {
13  fprintf(stderr, "Memory error in Cdhc_watson_u2_exp\n");
14  exit(EXIT_FAILURE);
15  }
16 
17  for (i = 0; i < n; ++i) {
18  xcopy[i] = x[i];
19  mean += x[i];
20  }
21  mean /= n;
22 
23  qsort(xcopy, n, sizeof(double), Cdhc_dcmp);
24 
25  for (i = 0; i < n; ++i) {
26  fx = 1 - exp(-xcopy[i] / mean);
27  if (fx <= 1e-5)
28  fx = 1e-5;
29 
30  if (fx >= 0.99999)
31  fx = 0.99999;
32 
33  /* sum3 += 2 * (i + 1) * (log (fx) + log (1.0 - fx[n - i - 1])); */
34  fn2 = (2.0 * i + 1.0) / (2.0 * n);
35  sum4 += (fx - fn2) * (fx - fn2);
36  fn2 = (2.0 * (i + 1) - 1.0) / (2.0 * n);
37  zbar += fx;
38  }
39 
40  zbar /= n;
41  y[0] = (1.0 / (n * 12) + sum4) - n * (zbar - .5) * (zbar - .5);
42  y[0] *= 1.0 + 0.16 / n;
43 
44 #ifdef NOISY
45  fprintf(stdout, " TEST19 WU2(E) =%10.4f\n", y[0]);
46 #endif /* NOISY */
47 
48  free(xcopy);
49 
50  return y;
51 }
#define NULL
Definition: ccmath.h:32
int Cdhc_dcmp(const void *i, const void *j)
Definition: dcmp.c:1
float mean(IClass_statistics *statistics, int band)
Helper function for computing mean.
void * malloc(YYSIZE_T)
void free(void *)
double * Cdhc_watson_u2_exp(double *x, int n)
Definition: watsonue.c:6
#define x