/**
* 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;
}
}
public SerFunkSVDModel(
ImmutableMatrix umat,
ImmutableMatrix imat,
IdIndexMapping uidx,
IdIndexMapping iidx,
List<FeatureInfo> features) {
super(umat, imat, uidx, iidx);
featureInfo = ImmutableList.copyOf(features);
double[] means = new double[featureCount];
for (int f = featureCount - 1; f >= 0; f--) {
means[f] = featureInfo.get(f).getUserAverage();
}
averageUser = ImmutableVector.wrap(means);
}
static ImmutableVector makeValues(PreferenceDomain domain) {
if (!domain.hasPrecision()) {
throw new IllegalArgumentException("domain is not discrete");
}
final double min = domain.getMinimum();
final double max = domain.getMaximum();
final double prec = domain.getPrecision();
final double nv = (max - min) / prec;
int n = (int) nv;
if (Math.abs(nv - n) > 1.0e-6) {
n += 1; // one more to cover everything...
}
if (n == 0) {
throw new IllegalArgumentException("range has no elements");
}
double[] values = new double[n + 1];
for (int i = 0; i <= n; i++) {
values[i] = min + (prec * i);
}
return ImmutableVector.wrap(values);
}