geogebra.common.kernel.statistics.RegressionMath.java Source code

Java tutorial

Introduction

Here is the source code for geogebra.common.kernel.statistics.RegressionMath.java

Source

package geogebra.common.kernel.statistics;

import geogebra.common.kernel.geos.GeoElement;
import geogebra.common.kernel.geos.GeoList;
import geogebra.common.kernel.geos.GeoPoint;
import geogebra.common.main.App;

import org.apache.commons.math.linear.Array2DRowRealMatrix;
import org.apache.commons.math.linear.DecompositionSolver;
import org.apache.commons.math.linear.QRDecompositionImpl;
import org.apache.commons.math.linear.RealMatrix;

/* 
 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.
    
 */

/**
 * <pre>
 * <h3>RegressionMath:</h3>
 * 
 *  RegressionMath is a library of sums, determinants and parameter calculations
 *  used by the FitXxx[GeoList]:GeoFunction commands.
 *   
 *  Might be problems if callers are running in separate threads.
 *  Is this a problem?
 *  
 *  
 *  @author Hans-Petter Ulven
 *  @version 20.02.10
 *  Start  24.04.08
 *  Update 15.11.08:
 *        public det22(...),...,det44(...) for use in FitSin() and FitLogistic()
 *  Update 27.01.09:
 *       doPolyN():boolean
 *       getPar():double[]
 *       to serve the extending of FitPoly[...] to degree>=5
 *       Matrix operations based on Jama.
 *  Update 20.02.2010:
 *        Changed from JaMa to Apache matrix library
 *       See doPolyN()  
 *       Got rid of r=corrcoff(), not used. Exists as separate command now.
 *
 * <ul><b>--- Interface: ---</b>
 *<li>RegressionMath(GeoList)
 *<li>det33(...), det44(...)   determinants. (Faster than Gauss for n<5)
 *<li>doLinReg(),doQuadReg(),doCubicReg(),doQuartRet()
 *<li>doExpReg(),doLogReg(),doPowReg()
 *<li>getSigmaX(),getSigmaX2(),[getSigmaX3()..getSigmaX5()
 *<li>getSigmaY(),[getSigmaY2(),getSigmaXY(),getSigmaX2Y(),getSigmaX3Y(),getSigmaX4Y()]
 *<li>getP1(),getP2(),getP3(),getP4(),getP5()   //Parameters for regression function
 *<li>getR()    //regression coeffisient. (When users get regression, they will certainly ask for this...)
 *</ul>
 */

public final class RegressionMath {

    // private final boolean DEBUG = false; //24.04.08: false for release
    public final static int LINEAR = 1, QUAD = 2, CUBIC = 3, QUART = 4, EXP = 5, LOG = 6, POW = 7;

    // / --- Properties --- ///
    private boolean error = false;
    // private int regtype = LINEAR; //Default
    private double // r, //Reg-coeff
    p1, p2, p3, p4, p5, // Parameters
            sigmax, sigmax2, sigmax3, sigmax4, // Sums of x,x^2,...
            sigmax5, sigmax6, sigmax7, sigmax8, sigmay, sigmay2, sigmaxy, sigmax2y, sigmax3y, sigmax4y;
    private GeoList geolist;
    private double[] xlist;
    private double[] ylist;
    private int size;

    // 27.01.09:
    private double[][] marray, yarray; // For (M_T*M)*Par=(M_T*Y)
    private double[] pararray; // Parameter array

    // / --- Interface --- ///
    /** Constructor not needed */
    public RegressionMath() { // private: Safety measure to avoid wrong use
    }// Constructor

    public final double getP1() {
        return p1;
    }

    public final double getP2() {
        return p2;
    }

    public final double getP3() {
        return p3;
    }

    public final double getP4() {
        return p4;
    }

    public final double getP5() {
        return p5;
    }

    // public final double getR() {return r; }
    public final double getSigmaX() {
        return sigmax;
    }

    public final double getSigmaX2() {
        return sigmax2;
    }

    public final double getSigmaY() {
        return sigmay;
    }

    public final double getSigmaY2() {
        return sigmay2;
    }

    public final double getSigmaXy() {
        return sigmaxy;
    }

    // 27.01.09:
    /** Returns array with calculated parameters */
    public final double[] getPar() {
        return pararray;
    }

    /** Does the Polynom regression for degree > 4 */
    public final boolean doPolyN(GeoList gl, int degree) {
        error = false;
        geolist = gl;
        size = geolist.size();
        getPoints(); // getPoints from geolist
        if (error) {
            return false;
        }
        try {
            /*
             * Old Jama version: long time=System.currentTimeMillis();
             * makeMatrixArrays(degree); //make marray and yarray Matrix M=new
             * Matrix(marray); Matrix Y=new Matrix(yarray); Matrix
             * Par=M.solve(Y); //Par.print(3,3);
             * pararray=Par.getRowPackedCopy();
             * System.out.println(System.currentTimeMillis()-time);
             */
            makeMatrixArrays(degree); // make marray and yarray
            RealMatrix M = new Array2DRowRealMatrix(marray, false);
            DecompositionSolver solver = new QRDecompositionImpl(M).getSolver();
            // time=System.currentTimeMillis();
            RealMatrix Y = new Array2DRowRealMatrix(yarray, false);
            RealMatrix P = solver.solve(Y);

            pararray = P.getColumn(0);

            // System.out.println(System.currentTimeMillis()-time);
            // diff(pararray,par);
        } catch (Throwable t) {
            App.debug(t.toString());
            error = true;
        } // try-catch. ToDo: A bit more fine-grained error-handling...
        return !error;
    }// doPolyN()

    public final boolean doLinear(GeoList gl) {
        error = false;
        geolist = gl;
        size = geolist.size();
        getPoints(); // getPoints from geolist
        if (error) {
            return false;
        }
        doSums(LINEAR); // calculate neccessary sigmas
        if (error) {
            return false;
        }

        double n = det22(1.0d * size, sigmax, sigmax, sigmax2);
        if (Math.abs(n - 0.0d) < 1.0E-15d) {
            return false;
        }
        p1 = det22(sigmay, sigmax, sigmaxy, sigmax2) / n;
        p2 = det22(size, sigmay, sigmax, sigmaxy) / n;
        // r=corrCoeff();
        return true;
    }// doLinearReg(GeoList)

    public final boolean doQuad(GeoList gl) {
        error = false;
        geolist = gl;
        size = geolist.size();
        getPoints(); // getPoints from geolist
        if (error) {
            return false;
        }
        doSums(QUAD); // calculate neccessary sigmas
        if (error) {
            return false;
        }

        double n = det33(1.0d * size, sigmax, sigmax2, sigmax, sigmax2, sigmax3, sigmax2, sigmax3, sigmax4);

        if (Math.abs(n - 0.0d) < 1.0E-15d) {
            return false;
        }
        p1 = det33(sigmay, sigmax, sigmax2, sigmaxy, sigmax2, sigmax3, sigmax2y, sigmax3, sigmax4) / n;
        p2 = det33(1.0d * size, sigmay, sigmax2, sigmax, sigmaxy, sigmax3, sigmax2, sigmax2y, sigmax4) / n;
        p3 = det33(1.0d * size, sigmax, sigmay, sigmax, sigmax2, sigmaxy, sigmax2, sigmax3, sigmax2y) / n;
        // r=0.0d; // Not useful
        return true;
    }// doQuad(Geolist)

    public final boolean doCubic(GeoList gl) {
        error = false;
        geolist = gl;
        size = geolist.size();
        getPoints(); // getPoints from geolist
        if (error) {
            return false;
        }
        doSums(CUBIC); // calculate neccessary sigmas
        if (error) {
            return false;
        }

        double n = det44(1.0d * size, sigmax, sigmax2, sigmax3, sigmax, sigmax2, sigmax3, sigmax4, sigmax2, sigmax3,
                sigmax4, sigmax5, sigmax3, sigmax4, sigmax5, sigmax6);

        if (Math.abs(n - 0.0d) < 1.0E-15d) {
            return false;
        }
        p1 = det44(sigmay, sigmax, sigmax2, sigmax3, sigmaxy, sigmax2, sigmax3, sigmax4, sigmax2y, sigmax3, sigmax4,
                sigmax5, sigmax3y, sigmax4, sigmax5, sigmax6) / n;
        p2 = det44(size, sigmay, sigmax2, sigmax3, sigmax, sigmaxy, sigmax3, sigmax4, sigmax2, sigmax2y, sigmax4,
                sigmax5, sigmax3, sigmax3y, sigmax5, sigmax6) / n;
        p3 = det44(size, sigmax, sigmay, sigmax3, sigmax, sigmax2, sigmaxy, sigmax4, sigmax2, sigmax3, sigmax2y,
                sigmax5, sigmax3, sigmax4, sigmax3y, sigmax6) / n;
        p4 = det44(size, sigmax, sigmax2, sigmay, sigmax, sigmax2, sigmax3, sigmaxy, sigmax2, sigmax3, sigmax4,
                sigmax2y, sigmax3, sigmax4, sigmax5, sigmax3y) / n;
        // r=0.0d; // Not useful
        return true;
    }// doCubic(Geolist)

    public final boolean doQuart(GeoList gl) {
        error = false;
        geolist = gl;
        size = geolist.size();
        getPoints(); // getPoints from geolist
        if (error) {
            return false;
        }
        doSums(QUART); // calculate neccessary sigmas
        if (error) {
            return false;
        }

        double n = det55(1.0d * size, sigmax, sigmax2, sigmax3, sigmax4, sigmax, sigmax2, sigmax3, sigmax4, sigmax5,
                sigmax2, sigmax3, sigmax4, sigmax5, sigmax6, sigmax3, sigmax4, sigmax5, sigmax6, sigmax7, sigmax4,
                sigmax5, sigmax6, sigmax7, sigmax8);
        if (Math.abs(n - 0.0d) < 1.0E-15d) {
            return false;
        }
        p1 = det55(sigmay, sigmax, sigmax2, sigmax3, sigmax4, sigmaxy, sigmax2, sigmax3, sigmax4, sigmax5, sigmax2y,
                sigmax3, sigmax4, sigmax5, sigmax6, sigmax3y, sigmax4, sigmax5, sigmax6, sigmax7, sigmax4y, sigmax5,
                sigmax6, sigmax7, sigmax8) / n;
        p2 = det55(1.0d * size, sigmay, sigmax2, sigmax3, sigmax4, sigmax, sigmaxy, sigmax3, sigmax4, sigmax5,
                sigmax2, sigmax2y, sigmax4, sigmax5, sigmax6, sigmax3, sigmax3y, sigmax5, sigmax6, sigmax7, sigmax4,
                sigmax4y, sigmax6, sigmax7, sigmax8) / n;
        p3 = det55(1.0d * size, sigmax, sigmay, sigmax3, sigmax4, sigmax, sigmax2, sigmaxy, sigmax4, sigmax5,
                sigmax2, sigmax3, sigmax2y, sigmax5, sigmax6, sigmax3, sigmax4, sigmax3y, sigmax6, sigmax7, sigmax4,
                sigmax5, sigmax4y, sigmax7, sigmax8) / n;
        p4 = det55(1.0d * size, sigmax, sigmax2, sigmay, sigmax4, sigmax, sigmax2, sigmax3, sigmaxy, sigmax5,
                sigmax2, sigmax3, sigmax4, sigmax2y, sigmax6, sigmax3, sigmax4, sigmax5, sigmax3y, sigmax7, sigmax4,
                sigmax5, sigmax6, sigmax4y, sigmax8) / n;
        p5 = det55(1.0d * size, sigmax, sigmax2, sigmax3, sigmay, sigmax, sigmax2, sigmax3, sigmax4, sigmaxy,
                sigmax2, sigmax3, sigmax4, sigmax5, sigmax2y, sigmax3, sigmax4, sigmax5, sigmax6, sigmax3y, sigmax4,
                sigmax5, sigmax6, sigmax7, sigmax4y) / n;
        // r=0.0d; // Not useful
        return true;
    }// doQuart(Geolist)

    public final boolean doExp(GeoList gl) {
        error = false;
        geolist = gl;
        double y = 0.0d;
        size = geolist.size();
        getPoints(); // getPoints from geolist
        if (error) {
            return false;
        }
        if (size == 0) {
            return false;
        }
        double ySign = ylist[0] < 0 ? -1 : 1;
        // Transform y->ln(y):
        for (int i = 0; i < size; i++) {
            y = ylist[i] * ySign;
            if (y < 0.0d) { // log(minus)!
                return false;
            }
            ylist[i] = Math.log(y);
        } // for all y
        doSums(LINEAR); // calculate neccessary sigmas
        if (error) {
            return false;
        }

        double n = det22(1.0d * size, sigmax, sigmax, sigmax2);
        if (Math.abs(n - 0.0d) < 1.0E-15d) {
            return false;
        }
        p1 = det22(sigmay, sigmax, sigmaxy, sigmax2) / n;
        p2 = det22(size, sigmay, sigmax, sigmaxy) / n;
        // transform back:
        p1 = Math.exp(p1) * ySign;
        // r=corrCoeff();
        return true;
    }// doExp(GeoList)

    public final boolean doLog(GeoList gl) {
        error = false;
        geolist = gl;
        double x = 0.0d;
        size = geolist.size();
        getPoints(); // getPoints from geolist
        if (error) {
            return false;
        }
        // Transform x->ln(x):
        for (int i = 0; i < size; i++) {
            x = xlist[i];
            if (x < 0.0d) { // log(minus)!
                return false;
            }
            xlist[i] = Math.log(xlist[i]);
        } // for all x
        doSums(LINEAR); // calculate neccessary sigmas
        if (error) {
            return false;
        }

        double n = det22(1.0d * size, sigmax, sigmax, sigmax2);
        if (Math.abs(n - 0.0d) < 1.0E-15d) {
            return false;
        }
        p1 = det22(sigmay, sigmax, sigmaxy, sigmax2) / n;
        p2 = det22(size, sigmay, sigmax, sigmaxy) / n;
        // No transformation of p1 or p2 neccessary
        // r=corrCoeff();
        return true;
    }// doLog(GeoList)

    public final boolean doPow(GeoList gl) {
        error = false;
        geolist = gl;
        double x, y;
        size = geolist.size();
        getPoints(); // getPoints from geolist
        if (error) {
            return false;
        }
        if (size == 0) {
            return false;
        }
        double ySign = ylist[0] < 0 ? -1 : 1;
        // Transform y->ln(y) and x->ln(x):
        for (int i = 0; i < size; i++) {
            x = xlist[i];
            y = ylist[i] * ySign;
            if ((x < 0.0d) || (y < 0.0d)) { // log(minus)!
                return false;
            }
            xlist[i] = Math.log(x);
            ylist[i] = Math.log(y);
        } // for all x
        doSums(LINEAR); // calculate neccessary sigmas
        if (error) {
            return false;
        }

        double n = det22(1.0d * size, sigmax, sigmax, sigmax2);
        if (Math.abs(n - 0.0d) < 1.0E-15d) {
            return false;
        }
        p1 = det22(sigmay, sigmax, sigmaxy, sigmax2) / n;
        p2 = det22(size, sigmay, sigmax, sigmaxy) / n;
        // Transform back:
        p1 = Math.exp(p1) * ySign;
        // r=corrCoeff();
        return true;
    }// doPow(GeoList)

    public final static double det22( // 15.11.08: public for FitSin and
            // FitLogisticc
            double a11, double a12, double a21, double a22) {
        return a11 * a22 - a21 * a12;
    }// det22()

    public final static double det33(
            // 15.11.08: public for FitSin and FitLogisticc
            double a11, double a12, double a13, double a21, double a22, double a23, double a31, double a32,
            double a33) {
        return a11 * (a22 * a33 - a32 * a23) - a12 * (a21 * a33 - a31 * a23) + a13 * (a21 * a32 - a31 * a22);
    }// det33()

    public final static double det44(
            // 15.11.08: public for FitSin and FitLogisticc
            double a11, double a12, double a13, double a14, double a21, double a22, double a23, double a24,
            double a31, double a32, double a33, double a34, double a41, double a42, double a43, double a44) {
        return a11 * a22 * a33 * a44 - a11 * a22 * a34 * a43 - a11 * a23 * a32 * a44 + a11 * a23 * a42 * a34
                + a11 * a32 * a24 * a43 - a11 * a24 * a33 * a42 - a12 * a21 * a33 * a44 + a12 * a21 * a34 * a43
                + a12 * a31 * a23 * a44 - a12 * a31 * a24 * a43 - a12 * a23 * a41 * a34 + a12 * a41 * a24 * a33
                + a21 * a13 * a32 * a44 - a21 * a13 * a42 * a34 - a21 * a14 * a32 * a43 + a21 * a14 * a33 * a42
                - a13 * a22 * a31 * a44 + a13 * a22 * a41 * a34 + a13 * a31 * a24 * a42 - a13 * a32 * a41 * a24
                + a22 * a31 * a14 * a43 - a22 * a14 * a41 * a33 - a31 * a14 * a23 * a42 + a14 * a23 * a32 * a41;
    }// det44()

    public final static double det55(
            // 15.11.08: public for FitSin and FitLogisticc
            double a11, double a12, double a13, double a14, double a15, double a21, double a22, double a23,
            double a24, double a25, double a31, double a32, double a33, double a34, double a35, double a41,
            double a42, double a43, double a44, double a45, double a51, double a52, double a53, double a54,
            double a55) {
        return a11 * a22 * a33 * a44 * a55 - a11 * a22 * a33 * a45 * a54 - a11 * a22 * a34 * a43 * a55
                + a11 * a22 * a34 * a53 * a45 + a11 * a22 * a43 * a35 * a54 - a11 * a22 * a35 * a44 * a53
                - a11 * a23 * a32 * a44 * a55 + a11 * a23 * a32 * a45 * a54 + a11 * a23 * a42 * a34 * a55
                - a11 * a23 * a42 * a35 * a54 - a11 * a23 * a34 * a52 * a45 + a11 * a23 * a52 * a35 * a44
                + a11 * a32 * a24 * a43 * a55 - a11 * a32 * a24 * a53 * a45 - a11 * a32 * a25 * a43 * a54
                + a11 * a32 * a25 * a44 * a53 - a11 * a24 * a33 * a42 * a55 + a11 * a24 * a33 * a52 * a45
                + a11 * a24 * a42 * a35 * a53 - a11 * a24 * a43 * a52 * a35 + a11 * a33 * a42 * a25 * a54
                - a11 * a33 * a25 * a52 * a44 - a11 * a42 * a25 * a34 * a53 + a11 * a25 * a34 * a43 * a52
                - a12 * a21 * a33 * a44 * a55 + a12 * a21 * a33 * a45 * a54 + a12 * a21 * a34 * a43 * a55
                - a12 * a21 * a34 * a53 * a45 - a12 * a21 * a43 * a35 * a54 + a12 * a21 * a35 * a44 * a53
                + a12 * a31 * a23 * a44 * a55 - a12 * a31 * a23 * a45 * a54 - a12 * a31 * a24 * a43 * a55
                + a12 * a31 * a24 * a53 * a45 + a12 * a31 * a25 * a43 * a54 - a12 * a31 * a25 * a44 * a53
                - a12 * a23 * a41 * a34 * a55 + a12 * a23 * a41 * a35 * a54 + a12 * a23 * a51 * a34 * a45
                - a12 * a23 * a51 * a35 * a44 + a12 * a41 * a24 * a33 * a55 - a12 * a41 * a24 * a35 * a53
                - a12 * a41 * a33 * a25 * a54 + a12 * a41 * a25 * a34 * a53 - a12 * a24 * a33 * a51 * a45
                + a12 * a24 * a51 * a43 * a35 + a12 * a33 * a51 * a25 * a44 - a12 * a51 * a25 * a34 * a43
                + a21 * a13 * a32 * a44 * a55 - a21 * a13 * a32 * a45 * a54 - a21 * a13 * a42 * a34 * a55
                + a21 * a13 * a42 * a35 * a54 + a21 * a13 * a34 * a52 * a45 - a21 * a13 * a52 * a35 * a44
                - a21 * a14 * a32 * a43 * a55 + a21 * a14 * a32 * a53 * a45 + a21 * a14 * a33 * a42 * a55
                - a21 * a14 * a33 * a52 * a45 - a21 * a14 * a42 * a35 * a53 + a21 * a14 * a43 * a52 * a35
                + a21 * a32 * a15 * a43 * a54 - a21 * a32 * a15 * a44 * a53 - a21 * a15 * a33 * a42 * a54
                + a21 * a15 * a33 * a52 * a44 + a21 * a15 * a42 * a34 * a53 - a21 * a15 * a34 * a43 * a52
                - a13 * a22 * a31 * a44 * a55 + a13 * a22 * a31 * a45 * a54 + a13 * a22 * a41 * a34 * a55
                - a13 * a22 * a41 * a35 * a54 - a13 * a22 * a51 * a34 * a45 + a13 * a22 * a51 * a35 * a44
                + a13 * a31 * a24 * a42 * a55 - a13 * a31 * a24 * a52 * a45 - a13 * a31 * a42 * a25 * a54
                + a13 * a31 * a25 * a52 * a44 - a13 * a32 * a41 * a24 * a55 + a13 * a32 * a41 * a25 * a54
                + a13 * a32 * a24 * a51 * a45 - a13 * a32 * a51 * a25 * a44 + a13 * a41 * a24 * a52 * a35
                - a13 * a41 * a25 * a34 * a52 - a13 * a24 * a42 * a51 * a35 + a13 * a42 * a51 * a25 * a34
                + a22 * a31 * a14 * a43 * a55 - a22 * a31 * a14 * a53 * a45 - a22 * a31 * a15 * a43 * a54
                + a22 * a31 * a15 * a44 * a53 - a22 * a14 * a41 * a33 * a55 + a22 * a14 * a41 * a35 * a53
                + a22 * a14 * a33 * a51 * a45 - a22 * a14 * a51 * a43 * a35 + a22 * a41 * a15 * a33 * a54
                - a22 * a41 * a15 * a34 * a53 - a22 * a15 * a33 * a51 * a44 + a22 * a15 * a51 * a34 * a43
                - a31 * a14 * a23 * a42 * a55 + a31 * a14 * a23 * a52 * a45 + a31 * a14 * a42 * a25 * a53
                - a31 * a14 * a25 * a43 * a52 + a31 * a23 * a15 * a42 * a54 - a31 * a23 * a15 * a52 * a44
                - a31 * a15 * a24 * a42 * a53 + a31 * a15 * a24 * a43 * a52 + a14 * a23 * a32 * a41 * a55
                - a14 * a23 * a32 * a51 * a45 - a14 * a23 * a41 * a52 * a35 + a14 * a23 * a42 * a51 * a35
                - a14 * a32 * a41 * a25 * a53 + a14 * a32 * a51 * a25 * a43 + a14 * a41 * a33 * a25 * a52
                - a14 * a33 * a42 * a51 * a25 - a23 * a32 * a41 * a15 * a54 + a23 * a32 * a15 * a51 * a44
                + a23 * a41 * a15 * a34 * a52 - a23 * a15 * a42 * a51 * a34 + a32 * a41 * a15 * a24 * a53
                - a32 * a15 * a24 * a51 * a43 - a41 * a15 * a24 * a33 * a52 + a15 * a24 * a33 * a42 * a51;
    }// det55

    // / --- Private --- ///

    /* Do whatever sums neccessary */
    private final void doSums(int degree) { // do whatever sums neccessary
        double x, y, xx, xy;
        sigmax = sigmax2 = sigmax3 = sigmax4 = sigmax5 = sigmax6 = sigmax7 = sigmax8 = sigmaxy = sigmax2y = sigmax3y = sigmax4y = sigmay = sigmay2 = 0.0d;
        for (int i = 0; i < size; i++) {
            x = xlist[i];
            y = ylist[i];
            xx = x * x;
            xy = x * y; // save some calculations
            switch (degree) { // fall-through-switch
            case 4:
                sigmax4y += x * xx * xy;
                sigmax7 += xx * xx * xx * x;
                sigmax8 += xx * xx * xx * xx;
            case 3:
                sigmax3y += xx * xy;
                sigmax5 += xx * xx * x;
                sigmax6 += xx * xx * xx;
            case 2:
                sigmax2y += xx * y;
                sigmax3 += xx * x;
                sigmax4 += xx * xx;
            case 1:
                sigmay2 += y * y; // r only for linear
            default:
                sigmax += x;
                sigmax2 += xx;
                sigmaxy += xy;
                sigmay += y;
            }// switch
        } // for
    }// doSums(degree)

    /* Get points to local array */
    private final void getPoints() {
        // double x,y;
        double xy[] = new double[2];
        GeoElement geoelement;
        // GeoPoint geopoint;
        xlist = new double[size];
        ylist = new double[size];
        for (int i = 0; i < size; i++) {
            geoelement = geolist.get(i);
            if (geoelement.isGeoPoint()) {
                ((GeoPoint) geoelement).getInhomCoords(xy);
                xlist[i] = xy[0];
                ylist[i] = xy[1];
            } else {
                error = true;
                xlist[i] = 0.0d;
                ylist[i] = 0.0d;
            } // if
        } // for all points
    }// getPoints()

    // Make M with 1,x,x^2,... , and Y with y1,y2,.. for all datapoints
    private final void makeMatrixArrays(int degree) {
        marray = new double[size][degree + 1];
        yarray = new double[size][1]; // column matrix
        for (int i = 0; i < size; i++) {
            // Y:
            yarray[i][0] = ylist[i];
            // M:
            for (int j = 0; j < (degree + 1); j++) {
                marray[i][j] = Math.pow(xlist[i], j);
            } // for j (all degrees =columns in marray)
        } // for i (all datapoints = rows in marray, cols in yarray)

    }// makeMatrixArrays()

    // / --- DEBUG --- /// !!! Remember to comment out calls before distribution
    // !!!

    /*
     * //---SNIP START---
     * 
     * // Debug of 2D array public static void aprint(double[][] a){ int
     * cols=a.length; int rows=a[0].length; for(int r=0;r<rows;r++){ for(int
     * c=0;c<cols;c++){ System.out.print(a[c][r]+" "); }// System.out.println();
     * }// }//aprint()
     * 
     * //debug of 1D array public static void aprint(double[] a){ for(int
     * i=0;i<a.length;i++){ System.out.println(a[i]+"  "); } }//
     * 
     * // Differences between Jama and Apache Solution // Outside GeoGebra the
     * diffs are <E-14 // In GeoGebra other rounding results in diffs <E-10 //
     * Jama is twice as fast if small datasets and degrees, // Apache about the
     * same if things get big... public static void diff(double[] a, double[]
     * b){ int size=Math.min(a.length,b.length); double dif=0.0d; for(int
     * i=0;i<size;i++){ dif=a[i]-b[i]; if(dif>1.0E-10){
     * //System.out.println("TOO BIG DIFFERENCE???");}
     * System.out.println(Math.abs(dif)); }//if too big diff }//for all data
     * }//diff
     */// --- SNIP END
}// class RegressionMath