/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.lucene.search.similarities;
/**
* Standardized measure of distance from independence
* <p>
* Described as:
* "good at tasks that require high recall and high precision, especially
* against short queries composed of a few words as in the case of Internet
* searches"
* @lucene.experimental
*/
public class IndependenceStandardized extends Independence {
/**
* Sole constructor.
*/
public IndependenceStandardized() {}
@Override
public float score(float freq, float expected) {
return (freq - expected) / (float) Math.sqrt(expected);
}
@Override
public String toString() {
return "Standardized";
}
}