/* unconditional Gaussian mutual information, to be used in C code. */
double c_mig(double *xx, double *yy, int *num) {
double cor = c_fast_cor(xx, yy, num);
return - 0.5 * log(1 - cor * cor);
}/*C_MIG*/
/* parametric tests for Gaussian variables. */
static double ut_gaustests(SEXP xx, SEXP yy, int nobs, int ntests,
double *pvalue, double *df, test_e test) {
int i = 0;
double transform = 0, *xptr = NULL, *yptr = REAL(yy);
double xm = 0, ym = 0, xsd = 0, ysd = 0, statistic = 0;
/* compute the degrees of freedom for correlation and mutual information. */
if (test == COR)
*df = nobs - 2;
else if ((test == MI_G) || (test == MI_G_SH))
*df = 1;
if (((test == COR) && (*df < 1)) || ((test == ZF) && (nobs - 2 < 2))) {
/* if there are not enough degrees of freedom, return independence. */
warning("trying to do an independence test with zero degrees of freedom.");
*df = 0;
statistic = 0;
for (i = 0; i < ntests; i++)
pvalue[i] = 1;
return statistic;
}/*THEN*/
/* cache mean and variance. */
ym = c_mean(yptr, nobs);
ysd = c_sse(yptr, ym, nobs);
for (i = 0; i < ntests; i++) {
GAUSSIAN_SWAP_X();
statistic = c_fast_cor(xptr, yptr, nobs, xm, ym, xsd, ysd);
if (test == COR) {
transform = cor_t_trans(statistic, *df);
pvalue[i] = 2 * pt(fabs(transform), *df, FALSE, FALSE);
}/*THEN*/
else if (test == MI_G) {
statistic = 2 * nobs * cor_mi_trans(statistic);
pvalue[i] = pchisq(statistic, *df, FALSE, FALSE);
}/*THEN*/
else if (test == MI_G_SH) {
statistic *= 1 - cor_lambda(xptr, yptr, nobs, xm, ym, xsd, ysd, statistic);
statistic = 2 * nobs * cor_mi_trans(statistic);
pvalue[i] = pchisq(statistic, *df, FALSE, FALSE);
}/*THEN*/
else if (test == ZF) {
statistic = cor_zf_trans(statistic, (double)nobs - 2);
pvalue[i] = 2 * pnorm(fabs(statistic), 0, 1, FALSE, FALSE);
}/*THEN*/
}/*FOR*/
return statistic;
}/*UT_GAUSTESTS*/
/* conditional linear Gaussian mutual information test. */
static double ut_micg(SEXP xx, SEXP yy, int nobs, int ntests, double *pvalue,
double *df) {
int i = 0, xtype = 0, ytype = TYPEOF(yy), llx = 0, lly = 0;
double xm = 0, xsd = 0, ym = 0, ysd = 0, statistic = 0;
void *xptr = NULL, *yptr = NULL;
SEXP xdata;
if (ytype == INTSXP) {
/* cache the number of levels. */
lly = NLEVELS(yy);
yptr = INTEGER(yy);
}/*THEN*/
else {
/* cache mean and variance. */
yptr = REAL(yy);
ym = c_mean(yptr, nobs);
ysd = c_sse(yptr, ym, nobs);
}/*ELSE*/
for (i = 0; i < ntests; i++) {
xdata = VECTOR_ELT(xx, i);
xtype = TYPEOF(xdata);
if ((ytype == INTSXP) && (xtype == INTSXP)) {
/* if both nodes are discrete, the test reverts back to a discrete
* mutual information test. */
xptr = INTEGER(xdata);
llx = NLEVELS(xdata);
DISCRETE_SWAP_X();
statistic = 2 * nobs * c_chisqtest(xptr, llx, yptr, lly, nobs, df, MI);
pvalue[i] = pchisq(statistic, *df, FALSE, FALSE);
}/*THEN*/
else if ((ytype == REALSXP) && (xtype == REALSXP)) {
/* if both nodes are continuous, the test reverts back to a Gaussian
* mutual information test. */
xptr = REAL(xdata);
xm = c_mean(xptr, nobs);
xsd = c_sse(xptr, xm, nobs);
statistic = c_fast_cor(xptr, yptr, nobs, xm, ym, xsd, ysd);
*df = 1;
statistic = 2 * nobs * cor_mi_trans(statistic);
pvalue[i] = pchisq(statistic, *df, FALSE, FALSE);
}/*THEN*/
else {
if (xtype == INTSXP) {
xptr = INTEGER(xdata);
llx = NLEVELS(xdata);
ysd = sqrt(ysd / (nobs - 1));
statistic = 2 * nobs * c_micg(yptr, ym, ysd, xptr, llx, nobs);
*df = llx - 1;
pvalue[i] = pchisq(statistic, *df, FALSE, FALSE);
}/*THEN*/
else {
xptr = REAL(xdata);
xm = c_mean(xptr, nobs);
xsd = sqrt(c_sse(xptr, xm, nobs) / (nobs - 1));
statistic = 2 * nobs * c_micg(xptr, xm, xsd, yptr, lly, nobs);
*df = lly - 1;
pvalue[i] = pchisq(statistic, *df, FALSE, FALSE);
}/*ELSE*/
}/*THEN*/
}/*FOR*/
return statistic;
}/*UT_MICG*/
/* compute all the pairwise mutual information coefficients between the variables. */
void mi_matrix(double *mim, void **columns, int dim, int *nlevels, int *num,
void *cond, int *clevels, double *means, double *sse, int *est) {
int i = 0, j = 0;
switch(*est) {
case DISCRETE_MAXIMUM_LIKELIHOOD:
if (!cond) {
for (i = 0; i < dim; i++) {
for (j = i + 1; j < dim; j++) {
mim[UPTRI3(i + 1, j + 1, dim)] =
c_chisqtest(((int **)columns)[i], nlevels[i],
((int **)columns)[j], nlevels[j], *num, NULL, MI, FALSE);
}/*FOR*/
}/*FOR*/
}/*THEN*/
else {
for (i = 0; i < dim; i++) {
for (j = i + 1; j < dim; j++) {
mim[UPTRI3(i + 1, j + 1, dim)] =
c_cchisqtest(((int **)columns)[i], nlevels[i],
((int **)columns)[j], nlevels[j],
(int *)cond, *clevels, *num, NULL, MI, FALSE);
}/*FOR*/
}/*FOR*/
}/*ELSE*/
break;
case GAUSSIAN_MAXIMUM_LIKELIHOOD:
for (i = 0; i < dim; i++) {
for (j = i + 1; j < dim; j++) {
mim[UPTRI3(i + 1, j + 1, dim)] = cor_mi_trans(
c_fast_cor(((double **)columns)[i], ((double **)columns)[j], *num,
means[i], means[j], sse[i], sse[j]));
}/*FOR*/
}/*FOR*/
break;
}/*SWITCH*/
}/*MI_MATRIX*/
