/**
* The constructor of OrdRecParameter. It use the quantized values of rating to initialize t1
* and beta. Each threshold is initialized as the mean of two contiguous rating values. Since
* the index of quantizer is always an successive non-negative integer begin from 0, so t1 will
* initialize as 0.5, and the interval between two thresholds will be 1.
*
* @param qtz The quantizer for ratings
*/
private OrdRecModel(Quantizer qtz) {
qtzValues = qtz.getValues();
levelCount = qtzValues.length();
t1 = (qtzValues.get(0) + qtzValues.get(1)) / 2;
beta = Vector.createLength(levelCount - 2);
double tr = t1;
for (int i = 1; i <= beta.length(); i++) {
double trnext = (qtzValues.get(i) + qtzValues.get(i + 1)) * 0.5;
beta.set(i - 1, Math.log(trnext - tr));
tr = trnext;
}
}
