Distance.java

/*
 * Apache License
 * Version 2.0, January 2004
 * http://www.apache.org/licenses/
 *
 *    Copyright 2013 Aurelian Tutuianu
 *    Copyright 2014 Aurelian Tutuianu
 *    Copyright 2015 Aurelian Tutuianu
 *    Copyright 2016 Aurelian Tutuianu
 *
 *    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 rapaio.ml.common.distance;

import rapaio.data.Frame;
import rapaio.util.Tag;

import java.io.Serializable;

/**
 * Distance interface
 * <p>
 * Created by <a href="mailto:padreati@yahoo.com">Aurelian Tutuianu</a> on 9/23/15.
 */
public interface Distance extends Serializable {

    double distance(Frame s, int sRow, Frame t, int tRow, String... varNames);

    Tag<Distance> EUCLIDEAN = Tag.valueOf("euclidean",
            (Frame s, int sRow, Frame t, int tRow, String... varNames) -> {
                double total = 0;
                for (String varName : varNames) {
                    if (s.missing(sRow) || t.missing(tRow))
                        continue;
                    total += Math.pow(s.value(sRow, varName) - t.value(tRow, varName), 2);
                }
                return Math.sqrt(total);
            });
}