static double
ckendall(int k, int n, double **w) {
int i, u;
double s;
u = (Sint) (n * (n - 1) / 2);
if ((k < 0) || (k > u))
return(0);
if (w[n] == 0) {
w[n] = (double *) R_alloc(u + 1, sizeof(double));
memset(w[n], '\0', sizeof(double) * (u+1));
for (i = 0; i <= u; i++)
w[n][i] = -1;
}
if (w[n][k] < 0) {
if (n == 1)
w[n][k] = (k == 0);
else {
s = 0;
for (i = 0; i < n; i++)
s += ckendall(k - i, n - 1, w);
w[n][k] = s;
}
}
return(w[n][k]);
}
void
dkendall(Sint *len, double *x, Sint *n) {
Sint i;
double **w;
w = (double **) R_alloc(*n + 1, sizeof(double *));
for (i = 0; i < *len; i++)
if (fabs(x[i] - floor(x[i] + 0.5)) > 1e-7) {
x[i] = 0;
} else {
x[i] = ckendall((Sint)x[i], (Sint)*n) / gammafn(*n + 1, w);
}
}
static void
pkendall(int len, double *Q, double *P, int n)
{
int i, j;
double p, q;
double **w;
w = (double **) R_alloc(n + 1, sizeof(double *));
memset(w, '\0', sizeof(double*) * (n+1));
for (i = 0; i < len; i++) {
q = floor(Q[i] + 1e-7);
if (q < 0)
P[i] = 0;
else if (q > (n * (n - 1) / 2))
P[i] = 1;
else {
p = 0;
for (j = 0; j <= q; j++) p += ckendall(j, n, w);
P[i] = p / gammafn(n + 1);
}
}
}
void
pkendall(Sint *len, double *x, Sint *n) {
Sint i, j;
double p, q;
double **w;
w = (double **) R_alloc(*n + 1, sizeof(double *));
memset(w, '\0', sizeof(double*) * (*n+1));
for (i = 0; i < *len; i++) {
q = floor(x[i] + 1e-7);
if (q < 0)
x[i] = 0;
else if (q > (*n * (*n - 1) / 2))
x[i] = 1;
else {
p = 0;
for (j = 0; j <= q; j++) {
p += ckendall((Sint)j, (Sint)*n, w);
}
x[i] = p / gammafn(*n + 1);
}
}
}
