#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "local_proto.h"


double *watson_u2  (double *x, int n)
{
  double *xcopy, mean = 0.0, sdx = 0.0, sqrt2, zbar = 0.0; 
  double fn2, fx, sum4 = 0.0;
  static double y[2];
  int i;

  sqrt2 = sqrt ((double) 2.0);

  if ((xcopy = (double *) malloc (n * sizeof (double))) == NULL)
  {
      fprintf (stderr, "Memory error in anderson_darling\n");
      exit (EXIT_FAILURE);
  }

  for (i = 0; i < n; ++i)
  {
    xcopy[i] = x[i];
    mean += x[i];
    sdx += x[i] * x[i];
  }
  sdx = sqrt ((n * sdx - mean * mean) / (n * (n - 1)));
  mean /= n;

  qsort (xcopy, n, sizeof (double), dcmp);

  for (i = 0; i < n; ++i)
  {
    xcopy[i] = (xcopy[i] - mean) / sdx;
    fn2 = (2.0 * (i + 1) - 1.0) / (2.0 * n);
    fx= 0.5 + normp (xcopy[i] / sqrt2) / 2.0;

    if (fx <= 0.0)
      fx = 1e-5;

    if (fx >= 1.0)
      fx = 0.99999;

    zbar += fx;
    sum4 += (fx - fn2) * (fx - fn2);
  }

  zbar /= n;
  y[0] = (1.0 / (n * 12) + sum4) - n * (zbar - .5) * (zbar - .5);
  y[0] *= 0.5 / n + 1.0;

#ifdef NOISY
  fprintf (stdout,"  TEST6  WU2(N) =%10.4f\n", y[0]);
#endif				/* NOISY */

  free(xcopy);

  return y;
}
