/** Analogous to binaryFeatureSet */
private Set<Feature> numericFeatureSet(int start, int end, Instance otherInstance) {
Set<Feature> s = new HashSet<Feature>();
for (int i = start; i < end; i++) {
addAll(s, unitInstance[i].numericFeatureIterator());
}
if (otherInstance != null) addAll(s, otherInstance.numericFeatureIterator());
return s;
}
