net.myrrix.online.som.Node.java Source code

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Here is the source code for net.myrrix.online.som.Node.java

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/*
 * Copyright Myrrix Ltd
 *
 * 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 net.myrrix.online.som;

import java.util.Collections;
import java.util.List;

import com.google.common.collect.Lists;
import org.apache.commons.math3.util.Pair;

/**
 * Represents a node in the final self-organizing map, which has both a set of members and a "center"
 * representing the node's corresponding position in the input feature space. It also includes
 * a projection of the center into 3D space, which aids display of the node. For example a 2D
 * display of the node grid can color nodes by construing the 3D projection as red, green and blue
 * components.
 *
 * @author Sean Owen
 * @since 1.0
 */
public final class Node {

    private List<Pair<Double, Long>> assignedIDs;
    private final float[] center;
    private final float[] projection3D;

    Node(float[] initialCenter) {
        center = initialCenter;
        projection3D = new float[3];
    }

    /**
     * @return {@link Pair}s of input points assigned to this node, given as point's ID and a score
     *  indicating how close it is to the center (here, cosine similarity)
     */
    public List<Pair<Double, Long>> getAssignedIDs() {
        return assignedIDs == null ? Collections.<Pair<Double, Long>>emptyList() : assignedIDs;
    }

    void addAssignedID(Pair<Double, Long> assignedID) {
        if (assignedIDs == null) {
            assignedIDs = Lists.newArrayListWithCapacity(1);
        }
        assignedIDs.add(assignedID);
    }

    void clearAssignedIDs() {
        assignedIDs = null;
    }

    /**
     * @return point in input space that this node corresponds to
     */
    public float[] getCenter() {
        return center;
    }

    /**
     * @return random projection of {@link #getCenter()} into the unit 3D square (every element in [0,1]).
     */
    public float[] getProjection3D() {
        return projection3D;
    }

}