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 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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
 *
 * 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.
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package org.apache.ignite.examples.ml.tutorial;

import java.io.FileNotFoundException;
import org.apache.ignite.Ignite;
import org.apache.ignite.IgniteCache;
import org.apache.ignite.Ignition;
import org.apache.ignite.ml.dataset.feature.extractor.Vectorizer;
import org.apache.ignite.ml.dataset.feature.extractor.impl.DummyVectorizer;
import org.apache.ignite.ml.knn.classification.KNNClassificationModel;
import org.apache.ignite.ml.knn.classification.KNNClassificationTrainer;
import org.apache.ignite.ml.math.primitives.vector.Vector;
import org.apache.ignite.ml.preprocessing.Preprocessor;
import org.apache.ignite.ml.preprocessing.encoding.EncoderTrainer;
import org.apache.ignite.ml.preprocessing.encoding.EncoderType;
import org.apache.ignite.ml.preprocessing.imputing.ImputerTrainer;
import org.apache.ignite.ml.preprocessing.minmaxscaling.MinMaxScalerTrainer;
import org.apache.ignite.ml.preprocessing.normalization.NormalizationTrainer;
import org.apache.ignite.ml.selection.scoring.evaluator.Evaluator;
import org.apache.ignite.ml.selection.scoring.metric.classification.Accuracy;

/**
 * Change classification algorithm that was used in {@link Step_5_Scaling} from decision tree to kNN ({@link
 * KNNClassificationTrainer}) because sometimes this can be beneficial.
 * <p>
 * Code in this example launches Ignite grid and fills the cache with test data (based on Titanic passengers data).</p>
 * <p>
 * After that it defines preprocessors that extract features from an upstream data and perform other desired changes
 * over the extracted data.</p>
 * <p>
 * Then, it trains the model based on the processed data using kNN classification.</p>
 * <p>
 * Finally, this example uses {@link Evaluator} functionality to compute metrics from predictions.</p>
 */
public class Step_6_KNN {
    /**
     * Run example.
     */
    public static void main(String[] args) {
        System.out.println();
        System.out.println(">>> Tutorial step 6 (kNN) example started.");

        try (Ignite ignite = Ignition.start("examples/config/example-ignite.xml")) {
            try {
                IgniteCache<Integer, Vector> dataCache = TitanicUtils.readPassengers(ignite);

                // Extracts "pclass", "sibsp", "parch", "sex", "embarked", "age", "fare".
                final Vectorizer<Integer, Vector, Integer, Double> vectorizer
                    = new DummyVectorizer<Integer>(0, 3, 4, 5, 6, 8, 10).labeled(1);

                Preprocessor<Integer, Vector> strEncoderPreprocessor = new EncoderTrainer<Integer, Vector>()
                    .withEncoderType(EncoderType.STRING_ENCODER)
                    .withEncodedFeature(1)
                    .withEncodedFeature(6) // <--- Changed index here.
                    .fit(ignite,
                        dataCache,
                        vectorizer
                    );

                Preprocessor<Integer, Vector> imputingPreprocessor = new ImputerTrainer<Integer, Vector>()
                    .fit(ignite,
                        dataCache,
                        strEncoderPreprocessor
                    );

                Preprocessor<Integer, Vector> minMaxScalerPreprocessor = new MinMaxScalerTrainer<Integer, Vector>()
                    .fit(
                        ignite,
                        dataCache,
                        imputingPreprocessor
                    );

                Preprocessor<Integer, Vector> normalizationPreprocessor = new NormalizationTrainer<Integer, Vector>()
                    .withP(1)
                    .fit(
                        ignite,
                        dataCache,
                        minMaxScalerPreprocessor
                    );

                KNNClassificationTrainer trainer = new KNNClassificationTrainer()
                    .withK(1)
                    .withWeighted(true);

                // Train decision tree model.
                KNNClassificationModel mdl = trainer.fit(
                    ignite,
                    dataCache,
                    normalizationPreprocessor
                );

                System.out.println("\n>>> Trained model: " + mdl);

                double accuracy = Evaluator.evaluate(
                    dataCache,
                    mdl,
                    normalizationPreprocessor,
                    new Accuracy<>()
                );

                System.out.println("\n>>> Accuracy " + accuracy);
                System.out.println("\n>>> Test Error " + (1 - accuracy));

                System.out.println(">>> Tutorial step 6 (kNN) example completed.");
            }
            catch (FileNotFoundException e) {
                e.printStackTrace();
            }
        }
        finally {
            System.out.flush();
        }
    }
}
