Android example source code file (InstanceLearner.java)

This example Android source code file (InstanceLearner.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

arraylist, comparator, double, instance, instancelearner, learner, override, prediction, string, treemap, util

The InstanceLearner.java Android example source code

/*
 * Copyright (C) 2008-2009 The Android Open Source Project
 *
 * 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 android.gesture;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.TreeMap;

/**
 * An implementation of an instance-based learner
 */

class InstanceLearner extends Learner {
    private static final Comparator<Prediction> sComparator = new Comparator() {
        public int compare(Prediction object1, Prediction object2) {
            double score1 = object1.score;
            double score2 = object2.score;
            if (score1 > score2) {
                return -1;
            } else if (score1 < score2) {
                return 1;
            } else {
                return 0;
            }
        }
    };

    @Override
    ArrayList<Prediction> classify(int sequenceType, int orientationType, float[] vector) {
        ArrayList<Prediction> predictions = new ArrayList();
        ArrayList<Instance> instances = getInstances();
        int count = instances.size();
        TreeMap<String, Double> label2score = new TreeMap();
        for (int i = 0; i < count; i++) {
            Instance sample = instances.get(i);
            if (sample.vector.length != vector.length) {
                continue;
            }
            double distance;
            if (sequenceType == GestureStore.SEQUENCE_SENSITIVE) {
                distance = GestureUtils.minimumCosineDistance(sample.vector, vector, orientationType);
            } else {
                distance = GestureUtils.squaredEuclideanDistance(sample.vector, vector);
            }
            double weight;
            if (distance == 0) {
                weight = Double.MAX_VALUE;
            } else {
                weight = 1 / distance;
            }
            Double score = label2score.get(sample.label);
            if (score == null || weight > score) {
                label2score.put(sample.label, weight);
            }
        }

//        double sum = 0;
        for (String name : label2score.keySet()) {
            double score = label2score.get(name);
//            sum += score;
            predictions.add(new Prediction(name, score));
        }

        // normalize
//        for (Prediction prediction : predictions) {
//            prediction.score /= sum;
//        }

        Collections.sort(predictions, sComparator);

        return predictions;
    }
}