Java tutorial
/* 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.GeoBoolean; import geogebra.kernel.GeoElement; import geogebra.kernel.GeoList; import geogebra.kernel.GeoNumeric; import geogebra.kernel.GeoText; import geogebra.kernel.arithmetic.NumberValue; import org.apache.commons.math.MathException; import org.apache.commons.math.stat.descriptive.StatisticalSummaryValues; import org.apache.commons.math.stat.inference.TTestImpl; /** * Performs a two sample t-test of the difference of means. * * @author G. Sturr */ public class AlgoTTest2 extends AlgoElement { private static final long serialVersionUID = 1L; private GeoList geoList0, geoList1; //input private GeoNumeric mean0, mean1, sd0, sd1, n0, n1; //input private GeoText tail; //input private GeoBoolean pooled; //input private GeoList result; // output private TTestImpl tTestImpl; private double[] val0, val1; public AlgoTTest2(Construction cons, String label, GeoList geoList0, GeoList geoList1, GeoText tail, GeoBoolean pooled) { super(cons); this.geoList0 = geoList0; this.geoList1 = geoList1; this.tail = tail; this.pooled = pooled; result = new GeoList(cons); setInputOutput(); // for AlgoElement compute(); result.setLabel(label); } public AlgoTTest2(Construction cons, String label, GeoNumeric mean0, GeoNumeric mean1, GeoNumeric sd0, GeoNumeric sd1, GeoNumeric n0, GeoNumeric n1, GeoText tail, GeoBoolean pooled) { super(cons); this.mean0 = mean0; this.mean1 = mean1; this.sd0 = sd0; this.sd1 = sd1; this.n0 = n0; this.n1 = n1; this.tail = tail; this.pooled = pooled; result = new GeoList(cons); setInputOutput(); // for AlgoElement compute(); result.setLabel(label); } public String getClassName() { return "AlgoTTest2"; } protected void setInputOutput() { if (geoList0 != null) { input = new GeoElement[4]; input[0] = geoList0; input[1] = geoList1; input[2] = tail; input[3] = pooled; } else { input = new GeoElement[8]; input[0] = mean0; input[1] = mean1; input[2] = sd0; input[3] = sd1; input[4] = n0; input[5] = n1; input[6] = tail; input[7] = pooled; } output = new GeoElement[1]; output[0] = result; setDependencies(); // done by AlgoElement } public GeoList getResult() { return result; } private double adjustedPValue(double p, double testStatistic) { // two sided test if (tail.getTextString().equals("!=") || tail.getTextString().equals("")) return p; // one sided test else if ((tail.getTextString().equals(">") && testStatistic > 0) || (tail.getTextString().equals("<") && testStatistic < 0)) return p / 2; else return 1 - p / 2; } protected final void compute() { if (!(tail.getTextString().equals("<") || tail.getTextString().equals(">") || tail.getTextString().equals("!=") || tail.getTextString().equals(""))) { result.setUndefined(); return; } double p, testStat; // sample data input if (input.length == 4) { int size0 = geoList0.size(); if (!geoList0.isDefined() || size0 < 2) { result.setUndefined(); return; } int size1 = geoList1.size(); if (!geoList1.isDefined() || size1 < 2) { result.setUndefined(); return; } val0 = new double[size0]; val1 = new double[size1]; // load array from first sample for (int i = 0; i < size0; i++) { GeoElement geo0 = geoList0.get(i); if (geo0.isNumberValue()) { NumberValue num = (NumberValue) geo0; val0[i] = num.getDouble(); } else { result.setUndefined(); return; } } // load array from second sample for (int i = 0; i < size1; i++) { GeoElement geo1 = geoList1.get(i); if (geo1.isNumberValue()) { NumberValue num = (NumberValue) geo1; val1[i] = num.getDouble(); } else { result.setUndefined(); return; } } try { // get the test statistic and p if (tTestImpl == null) tTestImpl = new TTestImpl(); if (pooled.getBoolean()) { testStat = tTestImpl.homoscedasticT(val0, val1); p = tTestImpl.homoscedasticTTest(val0, val1); p = adjustedPValue(p, testStat); } else { testStat = tTestImpl.t(val0, val1); p = tTestImpl.tTest(val0, val1); p = adjustedPValue(p, testStat); } // put these results into the output list result.clear(); result.add(new GeoNumeric(cons, p)); result.add(new GeoNumeric(cons, testStat)); } catch (IllegalArgumentException e) { e.printStackTrace(); } catch (MathException e) { e.printStackTrace(); } // sample statistics input } else { // check for valid stand. deviation and sample size if (sd0.getDouble() < 0 || sd1.getDouble() < 0 || n0.getDouble() < 2 || n1.getDouble() < 2) { result.setUndefined(); return; } StatisticalSummaryValues sumStats0 = new StatisticalSummaryValues(mean0.getDouble(), sd0.getDouble() * sd0.getDouble(), (long) n0.getDouble(), -1, -1, -1); StatisticalSummaryValues sumStats1 = new StatisticalSummaryValues(mean1.getDouble(), sd1.getDouble() * sd1.getDouble(), (long) n1.getDouble(), -1, -1, -1); try { // get the test statistic and p if (tTestImpl == null) tTestImpl = new TTestImpl(); if (pooled.getBoolean()) { testStat = tTestImpl.homoscedasticT(sumStats0, sumStats1); p = tTestImpl.homoscedasticTTest(sumStats0, sumStats1); p = adjustedPValue(p, testStat); } else { testStat = tTestImpl.t(sumStats0, sumStats1); p = tTestImpl.tTest(sumStats0, sumStats1); p = adjustedPValue(p, testStat); } // put these results into the output list result.clear(); result.add(new GeoNumeric(cons, p)); result.add(new GeoNumeric(cons, testStat)); } catch (IllegalArgumentException e) { e.printStackTrace(); } catch (MathException e) { e.printStackTrace(); } } } }