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Provides common utility functions

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/*
 * Copyright (c) CQSE GmbH
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.conqat.lib.commons.datamining;

import java.io.Serializable;
import java.util.Comparator;
import java.util.Set;

import org.conqat.lib.commons.collections.CollectionUtils;

/**
 * An association rule is of the form I -> j, where I is a set of items and j is an item. The rule
 * means that if all items of I appear in a shopping basket, then j is "likely" to appear in that
 * basket as well. Likely is defined by the confidence which is computed as the ratio between the
 * number of baskets containing both I and j and the number of baskets that contain I.
 */
public class AssociationRule implements Serializable {

	/** Version used for serialization. */
	private static final long serialVersionUID = 1;

	/** The item set (i.e. the I in I->j) */
	private Set itemSet;

	/** The associated item (i.e. the j in I->j) */
	private T associatedItem;

	/** The confidence level [0..1] */
	private double confidence;

	public AssociationRule(Set itemSet, T associatedItem, double confidence) {
		this.itemSet = itemSet;
		this.associatedItem = associatedItem;
		this.confidence = confidence;
	}

	/** Returns the item set */
	public Set getItemSet() {
		return itemSet;
	}

	/** Returns the associated item */
	public T getAssociatedItem() {
		return associatedItem;
	}

	/** Returns the confidence. */
	public double getConfidence() {
		return confidence;
	}

	/** {@inheritDoc} */
	@Override
	public String toString() {
		return CollectionUtils.sort(itemSet, new Comparator() {

			@Override
			public int compare(T t1, T t2) {
				return t1.toString().compareTo(t2.toString());
			}
		}).toString() + " -> " + associatedItem + " (" + confidence + ")";
	}
}