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#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "local_proto.h"
double *dmax(double *x, int n)
{
static double y[2];
double *xcopy, sqrt2, sqrtn, mean = 0.0, sdx = 0.0, fx;
double dp, dp_max, dm, dm_max;
int i;
if ((xcopy = (double *)malloc(n * sizeof(double))) == NULL) {
fprintf(stderr, "Memory error in dmax\n");
exit(EXIT_FAILURE);
}
sqrt2 = sqrt((double)2.0);
sqrtn = sqrt((double)n);
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 - 1.0)));
mean /= n;
qsort(xcopy, n, sizeof(double), dcmp);
for (i = 0; i < n; ++i) {
xcopy[i] = (xcopy[i] - mean) / sdx;
fx = 0.5 + normp(xcopy[i] / sqrt2) / 2.0;
if (fx <= 1e-5)
fx = 1e-5;
if (fx >= 0.99999)
fx = 0.99999;
dp = (double)(i + 1) / (double)n - fx;
dm = fx - i / (double)n;
if (i == 0 || dp > dp_max)
dp_max = dp;
if (i == 0 || dm > dm_max)
dm_max = dm;
}
y[0] = dp_max;
y[1] = dm_max;
free(xcopy);
return y;
}
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