GRASS Programmer's Manual
6.4.2(2012)
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00001 #include <stdio.h> 00002 #include <stdlib.h> 00003 #include <math.h> 00004 #include "local_proto.h" 00005 00006 00007 double *watson_u2(double *x, int n) 00008 { 00009 double *xcopy, mean = 0.0, sdx = 0.0, sqrt2, zbar = 0.0; 00010 double fn2, fx, sum4 = 0.0; 00011 static double y[2]; 00012 int i; 00013 00014 sqrt2 = sqrt((double)2.0); 00015 00016 if ((xcopy = (double *)malloc(n * sizeof(double))) == NULL) { 00017 fprintf(stderr, "Memory error in anderson_darling\n"); 00018 exit(EXIT_FAILURE); 00019 } 00020 00021 for (i = 0; i < n; ++i) { 00022 xcopy[i] = x[i]; 00023 mean += x[i]; 00024 sdx += x[i] * x[i]; 00025 } 00026 sdx = sqrt((n * sdx - mean * mean) / (n * (n - 1))); 00027 mean /= n; 00028 00029 qsort(xcopy, n, sizeof(double), dcmp); 00030 00031 for (i = 0; i < n; ++i) { 00032 xcopy[i] = (xcopy[i] - mean) / sdx; 00033 fn2 = (2.0 * (i + 1) - 1.0) / (2.0 * n); 00034 fx = 0.5 + normp(xcopy[i] / sqrt2) / 2.0; 00035 00036 if (fx <= 0.0) 00037 fx = 1e-5; 00038 00039 if (fx >= 1.0) 00040 fx = 0.99999; 00041 00042 zbar += fx; 00043 sum4 += (fx - fn2) * (fx - fn2); 00044 } 00045 00046 zbar /= n; 00047 y[0] = (1.0 / (n * 12) + sum4) - n * (zbar - .5) * (zbar - .5); 00048 y[0] *= 0.5 / n + 1.0; 00049 00050 #ifdef NOISY 00051 fprintf(stdout, " TEST6 WU2(N) =%10.4f\n", y[0]); 00052 #endif /* NOISY */ 00053 00054 free(xcopy); 00055 00056 return y; 00057 }