/* initialize a three-dimensional contingency table and the marginals. */
void fill_3d_table(int *xx, int *yy, int *zz, int ****n, int ***ni, int ***nj,
int **nk, int llx, int lly, int llz, int num) {
int i = 0, j = 0, k = 0;
*n = alloc3dcont(llz, llx, lly);
*ni = alloc2dcont(llz, llx);
*nj = alloc2dcont(llz, lly);
*nk = alloc1dcont(llz);
/* compute the joint frequency of x, y, and z. */
for (k = 0; k < num; k++)
(*n)[zz[k] - 1][xx[k] - 1][yy[k] - 1]++;
/* compute the marginals. */
for (i = 0; i < llx; i++)
for (j = 0; j < lly; j++)
for (k = 0; k < llz; k++) {
(*ni)[k][i] += (*n)[k][i][j];
(*nj)[k][j] += (*n)[k][i][j];
(*nk)[k] += (*n)[k][i][j];
}/*FOR*/
}/*FILL_3D_TABLE*/
/* conditional mutual information, to be used in C code. */
double c_cmi(int *xx, int *llx, int *yy, int *lly, int *zz, int *llz, int *num) {
int i = 0, j = 0, k = 0;
int ***n = NULL, **ni = NULL, **nj = NULL, *nk = NULL;
double res = 0;
/* initialize the contingency table and the marginal frequencies. */
n = alloc3dcont(*llx, *lly, *llz);
ni = alloc2dcont(*llx, *llz);
nj = alloc2dcont(*lly, *llz);
nk = alloc1dcont(*llz);
/* compute the joint frequency of x, y, and z. */
for (k = 0; k < *num; k++) {
n[xx[k] - 1][yy[k] - 1][zz[k] - 1]++;
}/*FOR*/
/* compute the marginals. */
for (i = 0; i < *llx; i++)
for (j = 0; j < *lly; j++)
for (k = 0; k < *llz; k++) {
ni[i][k] += n[i][j][k];
nj[j][k] += n[i][j][k];
nk[k] += n[i][j][k];
}/*FOR*/
/* compute the conditional mutual information from the joint and
marginal frequencies. */
for (i = 0; i < *llx; i++)
for (j = 0; j < *lly; j++)
for (k = 0; k < *llz; k++)
res += MI_PART(n[i][j][k], ni[i][k], nj[j][k], nk[k]);
res = res/(*num);
return res;
}/*C_CMI*/
