smile.math.distance.LeeDistance Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2010 Haifeng Li
*
* 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 smile.math.distance;
/**
* In coding theory, the Lee distance is a distance between two strings
* x1x2...xn and y1y2...yn
* of equal length n over the q-ary alphabet {0,1,...,q-1} of size q ≥ 2, defined as
*
* sum min(|xi-yi|, q-|xi-yi|)
*
* If q = 2 or q = 3 the Lee distance coincides with the Hamming distance.
* @author Haifeng Li
*/
public class LeeDistance implements Metric {
private int q;
/**
* Constructor with a given size q of alphabet.
* @param q the size of q-ary alphabet.
*/
public LeeDistance(int q) {
if (q < 2)
throw new IllegalArgumentException(String.format("The size of q-ary alphabet has to be larger than 1: q = %d", q));
this.q = q;
}
@Override
public String toString() {
return String.format("Lee distance (q = %d)", q);
}
@Override
public double d(int[] x, int[] y) {
if (x.length != y.length)
throw new IllegalArgumentException(String.format("Arrays have different length: x[%d], y[%d]", x.length, y.length));
int dist = 0;
for (int i = 0; i < x.length; i++) {
double d = Math.abs(x[i] - y[i]);
dist += Math.min(d, q-d);
}
return dist;
}
}