package com.blazebit.ai.decisiontree.impl;
import com.blazebit.ai.decisiontree.Attribute;
import com.blazebit.ai.decisiontree.AttributeValue;
import com.blazebit.ai.decisiontree.DecisionNode;
import com.blazebit.ai.decisiontree.DecisionNodeFactory;
import com.blazebit.ai.decisiontree.DiscreteAttribute;
import com.blazebit.ai.decisiontree.Example;
import com.blazebit.ai.decisiontree.Item;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
/**
*
* @author Christian Beikov
*/
public class DiscreteDecisionNode<T> implements DecisionNode<T> {
private final Attribute attribute;
private final Map<AttributeValue, DecisionNode<T>> children;
public DiscreteDecisionNode(final DecisionNodeFactory decisionNodeFactory, final DiscreteAttribute attribute, final Set<Example<T>> examples) {
this.attribute = attribute;
final Set<AttributeValue> attributeValues = attribute.getValues();
final Map<AttributeValue, Set<Example<T>>> exampleMap = new HashMap<AttributeValue, Set<Example<T>>>(attributeValues.size() + 1);
/* Fill values */
for (final Example<T> example : examples) {
final AttributeValue attributeValue = example.getValues().get(attribute);
Set<Example<T>> set = exampleMap.get(attributeValue);
if(set == null){
set = new HashSet<Example<T>>();
exampleMap.put(attributeValue, set);
}
set.add(example);
}
final Map<AttributeValue, DecisionNode<T>> localChildren = new HashMap<AttributeValue, DecisionNode<T>>(attributeValues.size() + 1);
/* Select next attribute for each attribute value */
for (final Map.Entry<AttributeValue, Set<Example<T>>> entry : exampleMap.entrySet()) {
localChildren.put(entry.getKey(), decisionNodeFactory.createNode(attribute, entry.getValue()));
}
this.children = localChildren;
}
@Override
public Attribute getAttribute() {
return attribute;
}
@Override
public Set<T> apply(final Item item) {
final AttributeValue value = item.getValues().get(attribute);
if (value == null) {
/* If no value exists for the current attribute, use the results of all the children */
final Set<T> results = new HashSet<T>();
for (final DecisionNode<T> node : children.values()) {
results.addAll(node.apply(item));
}
return results;
} else {
final DecisionNode<T> node = children.get(value);
if (node == null) {
return Collections.emptySet();
} else {
return node.apply(item);
}
}
}
@Override
public T applySingle(final Item item) {
final AttributeValue value = item.getValues().get(attribute);
if (value == null) {
/* If no value exists for the current attribute, use the results of all the children */
T result = null;
for (final DecisionNode<T> node : children.values()) {
final T tempResult = node.applySingle(item);
if(result == null){
result = tempResult;
}else if(tempResult != null){
throw new IllegalArgumentException("Ambigious result for the given item!");
}
}
return result;
} else {
final DecisionNode<T> node = children.get(value);
if (node == null) {
return null;
} else {
return node.applySingle(item);
}
}
}
}