DeltaTransformer.java

package pl.piotrsukiennik.whowhen.processer.transformer;

import pl.piotrsukiennik.whowhen.shared.util.math.MeanCalculator;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * @author Piotr Sukiennik
 */
public class DeltaTransformer extends AbstractFeatureVectorsTransformer {

    private int range;

    @Override
    public List<double[]> transform( List<double[]> features ) {
        List<double[]> output = new ArrayList<double[]>();
        double[][] window = new double[2 * range][];
        int featuresLen = features.size();
        for ( int i = 0; i < featuresLen; i++ ) {
            for ( int wi = 0, step = 1; wi < 2 * range; wi++, step++ ) {
                window[wi] = Arrays.copyOfRange( features.get( Math.min( Math.max( 0, i - step ), featuresLen - 1 ) ), getColumnsFrom(), getColumnsTo() );
                window[++wi] = Arrays.copyOfRange( features.get( Math.min( Math.max( 0, i + step ), featuresLen - 1 ) ), getColumnsFrom(), getColumnsTo() );
            }
            double[] featuresArray = features.get( i );
            double[] delta = MeanCalculator.calculateMean( Arrays.asList( window ), MeanCalculator.MeanMethod.ARITHMETIC );
            double[] featuresOutput = new double[featuresArray.length * 2];
            System.arraycopy( featuresArray, 0, featuresOutput, 0, featuresArray.length );
            System.arraycopy( delta, 0, featuresOutput, featuresArray.length, delta.length );
            output.add( featuresOutput );
        }
        return output;
    }

    public int getRange() {
        return range;
    }

    public void setRange( int range ) {
        this.range = range;
    }


    public static void main( String... args ) {
        DeltaTransformer deltaTransformer = new DeltaTransformer();
        deltaTransformer.setRange( 2 );
        for ( double[] doubles : deltaTransformer.transform( new ArrayList<double[]>() {{
            add( new double[] { .1, .2, .3, .4 } );
            add( new double[] { .1, .2, .3, .4 } );
            add( new double[] { .1, .2, .3, .4 } );
            add( new double[] { .1, .2, .3, .4 } );
            add( new double[] { .1, .2, .3, .4 } );
            add( new double[] { .1, .2, .3, .4 } );
            add( new double[] { .1, .2, .3, .4 } );
            add( new double[] { .1, .2, .3, .4 } );
            add( new double[] { .1, .2, .3, .4 } );
        }} ) ) {
            System.out.println( Arrays.toString( doubles ) );
        }
    }


}