com.cloudera.oryx.kmeans.common.Centers.java Source code

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Here is the source code for com.cloudera.oryx.kmeans.common.Centers.java

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/*
 * Copyright (c) 2013, Cloudera, Inc. All Rights Reserved.
 *
 * Cloudera, Inc. 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
 *
 * This software 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 com.cloudera.oryx.kmeans.common;

import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.Sets;
import org.apache.commons.math3.linear.RealVector;

/**
 * Represents a collection of {@code Vector} instances that act as the centers of
 * a set of clusters, as in a k-means model.
 */
public final class Centers implements Iterable<RealVector> {

    // The vectors, where each vector is the center of a particular cluster
    private final List<RealVector> centers;

    /**
     * Create a new instance from the given points. Any duplicate
     * points in the arg list will be removed.
     * 
     * @param points The points
     * @throws IllegalArgumentException if no points are given
     */
    public Centers(RealVector... points) {
        this(Arrays.asList(points));
    }

    /**
     * Create a new instance from the given points. Any duplicate
     * points in the {@code Iterable} instance will be removed.
     * 
     * @param points The points
     * @throws IllegalArgumentException if the input is empty
     */
    public Centers(Iterable<RealVector> points) {
        this.centers = ImmutableList.copyOf(Sets.newLinkedHashSet(points));
    }

    /**
     * Returns the number of points in this instance.
     */
    public int size() {
        return centers.size();
    }

    /**
     * Returns the {@code Vector} at the given index.
     */
    public RealVector get(int index) {
        return centers.get(index);
    }

    public boolean contains(RealVector vec) {
        return centers.contains(vec);
    }

    @Override
    public Iterator<RealVector> iterator() {
        return centers.iterator();
    }

    /**
     * Construct a new {@code Centers} object made up of the given {@code Vector}
     * and the points contained in this instance.
     * 
     * @param point The new point
     * @return A new {@code Centers} instance
     */
    public Centers extendWith(RealVector point) {
        return new Centers(Iterables.concat(centers, ImmutableList.of(point)));
    }

    /**
     * Returns the minimum squared Euclidean distance between the given
     * {@code Vector} and a point contained in this instance.
     * 
     * @param point The point
     * @return The minimum squared Euclidean distance from the point 
     */
    public Distance getDistance(RealVector point) {
        double min = Double.POSITIVE_INFINITY;
        int index = -1;
        for (int i = 0; i < centers.size(); i++) {
            RealVector c = centers.get(i);
            double distance = c.getDistance(point);
            double distanceSquared = distance * distance;
            if (distanceSquared < min) {
                min = distanceSquared;
                index = i;
            }
            min = Math.min(min, distance * distance);
        }
        return new Distance(min, index);
    }

    @Override
    public boolean equals(Object other) {
        if (!(other instanceof Centers)) {
            return false;
        }
        Centers c = (Centers) other;
        return centers.containsAll(c.centers) && c.centers.containsAll(centers);
    }

    @Override
    public int hashCode() {
        int hc = 0;
        for (RealVector center : centers) {
            hc += center.hashCode();
        }
        return hc;
    }

    @Override
    public String toString() {
        return centers.toString();
    }
}