com.aliasi.util.Distance Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of aliasi-lingpipe Show documentation

This is the original Lingpipe: http://alias-i.com/lingpipe/web/download.html There were not made any changes to the source code.

There is a newer version: 4.1.2-JL1.0

Show newest version

/*
 * 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.util;


/**
 * The Distance interface provides a general method for
 * defining distances between two objects.  Distance is a kind of
 * dissimilarity measure, because the larger the distance between two
 * objects, the less similar they are.  The distance interface
 * provides a single method {@link #distance(Object,Object)} returning
 * the distance between objects.
 *
 * A proper distance is said to form a metric if it satisfies the
 * following four properties:
 *
 * 

 *  Positive:  distance(x,y) >= 0
 * 
 Self Distance Zero:  distance(x,x) = 0
 * 
 Symmetric: distance(x,y) = distance(y,x)
 * 
 Triangle Inequaltiy: distance(x,y) + distance(y,z) >= distance(x,z)
 * 
 *
 * For example, the Euclidean distance between vectors is
 * a proper metric.
 *
 * 
 * distance(x,y) = sqrt(Σ_{_i} (x[i] * y[i])²)
 *
 * as is the Manhattan metric, or taxicab distance:
 *
 *  * distance(x,y) = Σ_{_i} abs(x[i] - y[i])
 *
 * Cosine is also popular for vectors:
 *
 *  * distance(x,y) = dotProduct(x,y) / (length(x) * length(y))
 *
 * A good introduction to distance may be found at:
 *
 * 

 * Wikipedia: Distance
 * 
 *
 * @author  Bob Carpenter
 * @version 3.0
 * @since   LingPipe3.0
 * @param  the type of objects over which distances are defined
 */
public interface Distance {

    /**
     * Returns the distance between the specified pair of objects.
     *
     * @param e1 First object.
     * @param e2 Second object.
     * @return Distance between the two objects.
     */
    public double distance(E e1, E e2);

}