package io.sigpipe.sing.stat;

import java.util.List;

import org.apache.commons.math3.util.FastMath;

import io.sigpipe.sing.dataset.feature.Feature;

public class SquaredError {

    private RunningStatistics sqErrs = new RunningStatistics();
    private RunningStatistics actualStats = new RunningStatistics();
    private RunningStatistics predictedStats = new RunningStatistics();

    public SquaredError(List<Feature> actual, List<Feature> predicted) {
        if (actual.size() != predicted.size()) {
            throw new IllegalArgumentException(
                    "List sizes must be equal");
        }

        for (int i = 0; i < actual.size(); ++i) {
            Feature a = actual.get(i);
            Feature p = predicted.get(i);
            this.put(a, p);
        }
    }

    public void put(Feature actual, Feature predicted) {
        this.put(actual.getDouble(), predicted.getDouble());
    }

    public void put(double actual, double predicted) {
        double err = actual - predicted;
        double p = FastMath.pow(err, 2.0);
        sqErrs.put(p);
        actualStats.put(actual);
        predictedStats.put(predicted);
    }

    public double RMSE() {
        return FastMath.sqrt(sqErrs.mean());
    }

    public double NRMSE() {
        return RMSE() / (actualStats.max() - actualStats.min());
    }

    public double CVRMSE() {
        return RMSE() / actualStats.mean();
    }

    public SummaryStatistics actualSummary() {
        return new SummaryStatistics(actualStats);
    }

    public SummaryStatistics predictedSummary() {
        return new SummaryStatistics(predictedStats);
    }

}

package io.sigpipe.sing.stat;

import java.util.List;

import org.apache.commons.math3.util.FastMath;

import io.sigpipe.sing.dataset.feature.Feature;

public class SquaredError {

    private RunningStatistics sqErrs = new RunningStatistics();
    private RunningStatistics actualStats = new RunningStatistics();
    private RunningStatistics predictedStats = new RunningStatistics();

    public SquaredError() {

    }

    public SquaredError(List<Feature> actual, List<Feature> predicted) {
        if (actual.size() != predicted.size()) {
            throw new IllegalArgumentException(
                    "List sizes must be equal");
        }

        for (int i = 0; i < actual.size(); ++i) {
            Feature a = actual.get(i);
            Feature p = predicted.get(i);
            this.put(a, p);
        }
    }

    public void put(Feature actual, Feature predicted) {
        this.put(actual.getDouble(), predicted.getDouble());
    }

    public void put(double actual, double predicted) {
        double err = actual - predicted;
        double p = FastMath.pow(err, 2.0);
        sqErrs.put(p);
        actualStats.put(actual);
        predictedStats.put(predicted);
    }

    public double RMSE() {
        return FastMath.sqrt(sqErrs.mean());
    }

    public double NRMSE() {
        return RMSE() / (actualStats.max() - actualStats.min());
    }

    public double CVRMSE() {
        return RMSE() / actualStats.mean();
    }

    public SummaryStatistics actualSummary() {
        return new SummaryStatistics(actualStats);
    }

    public SummaryStatistics predictedSummary() {
        return new SummaryStatistics(predictedStats);
    }

}

Allow empty instances