/**
* Digamma function (the first derivative of the logarithm of the gamma function).
*
* @param array - variational parameter
* @return
*/
static double[][] dirichletExpectation(double[][] array) {
int numRows = array.length;
int numCols = array[0].length;
double[] vector = new double[numRows];
Arrays.fill(vector, 0.0);
for (int k = 0; k < numRows; ++k) {
for (int w = 0; w < numCols; ++w) {
try {
vector[k] += array[k][w];
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
for (int k = 0; k < numRows; ++k) {
vector[k] = Gamma.digamma(vector[k]);
}
double[][] approx = new double[numRows][];
for (int k = 0; k < numRows; ++k) {
approx[k] = new double[numCols];
for (int w = 0; w < numCols; ++w) {
double z = Gamma.digamma(array[k][w]);
approx[k][w] = z - vector[k];
}
}
return approx;
}
static double[] dirichletExpectation(double[] array) {
double sum = 0;
for (double d : array) {
sum += d;
}
double d = Gamma.digamma(sum);
double[] result = new double[array.length];
for (int i = 0; i < array.length; ++i) {
result[i] = Gamma.digamma(array[i]) - d;
}
return result;
}
