GRASS Programmer's Manual  6.4.2(2012)
andrsnde.c
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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 *anderson_darling_exp(double *x, int n)
00008 {
00009     static double y[2];
00010     double sqrt2, mean = 0.0, *xcopy, fx, sum3 = 0.0;
00011     int i;
00012 
00013     if ((xcopy = (double *)malloc(n * sizeof(double))) == NULL) {
00014         fprintf(stderr, "Memory error in anderson_darling\n");
00015         exit(EXIT_FAILURE);
00016     }
00017 
00018     sqrt2 = sqrt((double)2.0);
00019 
00020     for (i = 0; i < n; ++i) {
00021         xcopy[i] = x[i];
00022         mean += x[i];
00023     }
00024     mean /= n;
00025     qsort(xcopy, n, sizeof(double), dcmp);
00026 
00027     for (i = 0; i < n; ++i) {
00028         fx = 1 - exp(-xcopy[i] / mean);
00029         sum3 += (2.0 * i + 1) * (log(fx) - xcopy[n - i - 1] / mean);
00030     }
00031 
00032     y[0] = (1.0 + 0.3 / n) * (-n - sum3 / n);
00033 #ifdef NOISY
00034     fprintf(stdout, "  TEST20 AD(E)  =%10.4f\n", y[0]);
00035 #endif /* NOISY */
00036 
00037     free(xcopy);
00038 
00039     return y;
00040 }
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