com.aliasi.matrix.CosineDistance Maven / Gradle / Ivy
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/*
* LingPipe v. 4.1.0
* Copyright (C) 2003-2011 Alias-i
*
* This program is licensed under the Alias-i Royalty Free License
* Version 1 WITHOUT ANY WARRANTY, without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the Alias-i
* Royalty Free License Version 1 for more details.
*
* You should have received a copy of the Alias-i Royalty Free License
* Version 1 along with this program; if not, visit
* http://alias-i.com/lingpipe/licenses/lingpipe-license-1.txt or contact
* Alias-i, Inc. at 181 North 11th Street, Suite 401, Brooklyn, NY 11211,
* +1 (718) 290-9170.
*/
package com.aliasi.matrix;
import com.aliasi.util.Proximity;
import java.io.Serializable;
/**
* The CosineDistance class implements proximity as
* vector cosine. Distance is defined as one minus the proximity.
*
* The vector cosine operation is defined in the vector interface,
* {@link Vector#cosine(Vector)}
*
* @author Bob Carpenter
* @version 3.1.3
* @since LingPipe3.1
*/
public class CosineDistance
implements Proximity,
Serializable {
static final long serialVersionUID = -8456511197031445244L;
/**
* A constant for the cosine distance. Because the distance
* function is thread safe, this single instance may be
* used wherever the cosine distance is needed.
*/
public static final CosineDistance DISTANCE
= new CosineDistance();
/**
* Construct a cosine proximity.
*/
public CosineDistance() {
/* empty constructor */
}
/**
* Returns one minus the proximity of the vectors.
*
*
* distance(v1,v2) = 1.0 - proximity(v1,v2)
*
* With this definition, distances run between 0 and 2,
* with identical vectors being at distance 0, orthogonal
* vectors at distance 1 and oppositive vectors at distance 2.
*
*
* @param v1 First vector.
* @param v2 Second vector.
* @return The negative cosine between the first and second vector.
*/
public double distance(Vector v1, Vector v2) {
return 1.0 / (1.0 + proximity(v1,v2));
}
/**
* Returns the cosine between the specified vectors. The
* proximity will be 1 if the vectors are identical in
* direction, 0 if they are orthogonal, and -1 if they
* are in opposite directions.
*
* @param v1 First vector.
* @param v2 Second vector.
* @return The cosine between the first and second vector.
*/
public double proximity(Vector v1, Vector v2) {
return v1.cosine(v2);
}
}