org.simmetrics.MultisetMetric Maven / Gradle / Ivy
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* #%L
* Simmetrics Core
* %%
* Copyright (C) 2014 - 2015 Simmetrics Authors
* %%
* 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.
* #L%
*/
package org.simmetrics;
import com.google.common.collect.Multiset;
import com.google.common.collect.Multisets;
/**
* Measures the similarity between two arbitrary multisets containing elements
* of the same type. The measurement results in a value between 0 and 1
* inclusive. A value of zero indicates that the sets are dissimilar, a value of
* 1 indicates they are similar.
*
*
* The elements in the multisets have to implement {@link Object#hashCode()} and
* {@link Object#equals(Object)}.
*
* The elements in the multisets may not be null if metric does not support null
* values.
*
* The similarity measure should be consistent with equals such that
* {@code a.equals(b) => compare(a,b) == 1.0}.
*
* The similarity measure should be reflexive such that
* {@code compare(a,a) == 1.0}.
*
* The similarity measure should be symmetric such that
* {@code compare(a,b) == compare(b,a)}.
*
* Implementations may not modify the contents of the multisets. Multisets should be
* treated as if wrapped by {@link Multisets#unmodifiableMultiset(Multiset)}.
*
* @param
* the type of elements contained in the sets
*
*/
public interface MultisetMetric extends Metric> {
/**
* Measures the similarity between multisets a and b. The measurement
* results in a value between 0 and 1 inclusive. A value of zero indicates
* that the sets are dissimilar, a value of 1 indicates they are similar.
*
* Results are undefined if {@code a} and {@code b} are based on different
* equivalence relations (as {@code HashMultiset} and {@code TreeMultiset}
* are).
*
* @param a
* multisets a to compare
* @param b
* multisets b to compare
* @return a value between 0 and 1 inclusive indicating similarity
* @throws NullPointerException
* when either a or b is null
*/
@Override
public float compare(Multiset a, Multiset b);
}