geogebra.kernel.statistics.AlgoTMeanEstimate.java Source code

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Here is the source code for geogebra.kernel.statistics.AlgoTMeanEstimate.java

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/* 
GeoGebra - Dynamic Mathematics for Everyone
http://www.geogebra.org
    
This file is part of GeoGebra.
    
This program is free software; you can redistribute it and/or modify it 
under the terms of the GNU General Public License as published by 
the Free Software Foundation.
    
 */

package geogebra.kernel.statistics;

import geogebra.kernel.AlgoElement;
import geogebra.kernel.Construction;
import geogebra.kernel.GeoElement;
import geogebra.kernel.GeoList;
import geogebra.kernel.GeoNumeric;
import geogebra.kernel.arithmetic.NumberValue;

import org.apache.commons.math.MathException;
import org.apache.commons.math.distribution.TDistributionImpl;
import org.apache.commons.math.stat.descriptive.SummaryStatistics;

/**
 * Calculates a one sample t-confidence interval estimate of a mean.
 * 
 * 
 * @author G. Sturr
 */
public class AlgoTMeanEstimate extends AlgoElement {

    private static final long serialVersionUID = 1L;
    private GeoList geoList; //input
    private GeoNumeric geoLevel, geoMean, geoSD, geoN; //input
    private GeoList result; // output   

    private double[] val;
    private double level, mean, sd, n, me;
    private SummaryStatistics stats;
    private TDistributionImpl tDist;

    public AlgoTMeanEstimate(Construction cons, String label, GeoList geoList, GeoNumeric geoLevel) {
        super(cons);
        this.geoList = geoList;
        this.geoLevel = geoLevel;
        this.geoMean = null;
        this.geoSD = null;
        this.geoN = null;

        result = new GeoList(cons);
        setInputOutput(); // for AlgoElement

        compute();
        result.setLabel(label);
    }

    public AlgoTMeanEstimate(Construction cons, String label, GeoNumeric geoMean, GeoNumeric geoSD, GeoNumeric geoN,
            GeoNumeric geoLevel) {
        super(cons);
        this.geoList = null;
        this.geoLevel = geoLevel;
        this.geoMean = geoMean;
        this.geoSD = geoSD;
        this.geoN = geoN;

        result = new GeoList(cons);
        setInputOutput(); // for AlgoElement

        compute();
        result.setLabel(label);
    }

    public String getClassName() {
        return "AlgoTMeanEstimate";
    }

    protected void setInputOutput() {

        if (geoList != null) {
            input = new GeoElement[2];
            input[0] = geoList;
            input[1] = geoLevel;

        } else {
            input = new GeoElement[4];
            input[0] = geoMean;
            input[1] = geoSD;
            input[2] = geoN;
            input[3] = geoLevel;
        }

        output = new GeoElement[1];
        output[0] = result;
        setDependencies(); // done by AlgoElement
    }

    public GeoList getResult() {
        return result;
    }

    private double getMarginOfError(double sd, double n, double confLevel) throws MathException {
        tDist = new TDistributionImpl(n - 1);
        double a = tDist.inverseCumulativeProbability((confLevel + 1d) / 2);
        return a * sd / Math.sqrt(n);
    }

    protected final void compute() {

        try {

            // get statistics from sample data input
            if (input.length == 2) {

                int size = geoList.size();
                if (!geoList.isDefined() || size < 2) {
                    result.setUndefined();
                    return;
                }

                val = new double[size];
                for (int i = 0; i < size; i++) {
                    GeoElement geo = geoList.get(i);
                    if (geo.isNumberValue()) {
                        NumberValue num = (NumberValue) geo;
                        val[i] = num.getDouble();

                    } else {
                        result.setUndefined();
                        return;
                    }
                }

                stats = new SummaryStatistics();
                for (int i = 0; i < val.length; i++) {
                    stats.addValue(val[i]);
                }

                n = stats.getN();
                sd = stats.getStandardDeviation();
                mean = stats.getMean();

            } else {

                mean = geoMean.getDouble();
                sd = geoSD.getDouble();
                n = geoN.getDouble();
            }

            level = geoLevel.getDouble();

            // validate statistics
            if (level < 0 || level > 1 || sd < 0 || n < 1) {
                result.setUndefined();
                return;
            }

            // get interval estimate 
            me = getMarginOfError(sd, n, level);

            // return list = {low limit, high limit, mean, margin of error, df }
            result.clear();
            boolean oldSuppress = cons.isSuppressLabelsActive();
            cons.setSuppressLabelCreation(true);
            result.add(new GeoNumeric(cons, mean - me));
            result.add(new GeoNumeric(cons, mean + me));
            //result.add(new GeoNumeric(cons, mean));
            //result.add(new GeoNumeric(cons, me));
            //result.add(new GeoNumeric(cons, n-1)); // df
            cons.setSuppressLabelCreation(oldSuppress);

        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (MathException e) {
            e.printStackTrace();
        }

    }

}