src/test/org/apache/commons/math/stat/regression/SimpleRegressionTest.java

/*
 * Copyright 2003-2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math.stat.regression;

import java.util.Random;

import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;
/**
 * Test cases for the TestStatistic class.
 *
 * @version $Revision$ $Date$
 */

public final class SimpleRegressionTest extends TestCase {

    /* 
     * NIST "Norris" refernce data set from 
     * http://www.itl.nist.gov/div898/strd/lls/data/LINKS/DATA/Norris.dat
     * Strangely, order is {y,x}
     */
    private double[][] data = { { 0.1, 0.2 }, {338.8, 337.4 }, {118.1, 118.2 }, 
            {888.0, 884.6 }, {9.2, 10.1 }, {228.1, 226.5 }, {668.5, 666.3 }, {998.5, 996.3 }, 
            {449.1, 448.6 }, {778.9, 777.0 }, {559.2, 558.2 }, {0.3, 0.4 }, {0.1, 0.6 }, {778.1, 775.5 }, 
            {668.8, 666.9 }, {339.3, 338.0 }, {448.9, 447.5 }, {10.8, 11.6 }, {557.7, 556.0 }, 
            {228.3, 228.1 }, {998.0, 995.8 }, {888.8, 887.6 }, {119.6, 120.2 }, {0.3, 0.3 }, 
            {0.6, 0.3 }, {557.6, 556.8 }, {339.3, 339.1 }, {888.0, 887.2 }, {998.5, 999.0 }, 
            {778.9, 779.0 }, {10.2, 11.1 }, {117.6, 118.3 }, {228.9, 229.2 }, {668.4, 669.1 }, 
            {449.2, 448.9 }, {0.2, 0.5 }
    };

    /* 
     * Correlation example from 
     * http://www.xycoon.com/correlation.htm
     */
    private double[][] corrData = { { 101.0, 99.2 }, {100.1, 99.0 }, {100.0, 100.0 }, 
            {90.6, 111.6 }, {86.5, 122.2 }, {89.7, 117.6 }, {90.6, 121.1 }, {82.8, 136.0 }, 
            {70.1, 154.2 }, {65.4, 153.6 }, {61.3, 158.5 }, {62.5, 140.6 }, {63.6, 136.2 }, 
            {52.6, 168.0 }, {59.7, 154.3 }, {59.5, 149.0 }, {61.3, 165.5 }
    };

    /*
     * From Moore and Mcabe, "Introduction to the Practice of Statistics"
     * Example 10.3 
     */
    private double[][] infData = { { 15.6, 5.2 }, {26.8, 6.1 }, {37.8, 8.7 }, {36.4, 8.5 },
            {35.5, 8.8 }, {18.6, 4.9 }, {15.3, 4.5 }, {7.9, 2.5 }, {0.0, 1.1 }
    };
    
    /*
     * Data with bad linear fit
     */
    private double[][] infData2 = { { 1, 1 }, {2, 0 }, {3, 5 }, {4, 2 },
            {5, -1 }, {6, 12 }
    };

    public SimpleRegressionTest(String name) {
        super(name);
    }

    public void setUp() {
    }

    public static Test suite() {
        TestSuite suite = new TestSuite(SimpleRegressionTest.class);
        suite.setName("BivariateRegression Tests");
        return suite;
    }

    public void testNorris() {
        SimpleRegression regression = new SimpleRegression();
        for (int i = 0; i < data.length; i++) {
            regression.addData(data[i][1], data[i][0]);
        }
        // Tests against certified values from  
        // http://www.itl.nist.gov/div898/strd/lls/data/LINKS/DATA/Norris.dat
        assertEquals("slope", 1.00211681802045, regression.getSlope(), 10E-12);
        assertEquals("slope std err", 0.429796848199937E-03,
                regression.getSlopeStdErr(),10E-12);
        assertEquals("number of observations", 36, regression.getN());
        assertEquals( "intercept", -0.262323073774029,
            regression.getIntercept(),10E-12);
        assertEquals("std err intercept", 0.232818234301152,
            regression.getInterceptStdErr(),10E-12);
        assertEquals("r-square", 0.999993745883712,
            regression.getRSquare(), 10E-12);
        assertEquals("SSR", 4255954.13232369,
            regression.getRegressionSumSquares(), 10E-9);
        assertEquals("MSE", 0.782864662630069,
            regression.getMeanSquareError(), 10E-10);
        assertEquals("SSE", 26.6173985294224,
            regression.getSumSquaredErrors(),10E-9);
        // ------------  End certified data tests
          
        assertEquals( "predict(0)",  -0.262323073774029,
            regression.predict(0), 10E-12);
        assertEquals("predict(1)", 1.00211681802045 - 0.262323073774029,
            regression.predict(1), 10E-12);
    }

    public void testCorr() {
        SimpleRegression regression = new SimpleRegression();
        regression.addData(corrData);
        assertEquals("number of observations", 17, regression.getN());
        assertEquals("r-square", .896123, regression.getRSquare(), 10E-6);
        assertEquals("r", -0.94663767742, regression.getR(), 1E-10);
    }

    public void testNaNs() {
        SimpleRegression regression = new SimpleRegression();
        assertTrue("intercept not NaN", Double.isNaN(regression.getIntercept()));
        assertTrue("slope not NaN", Double.isNaN(regression.getSlope()));
        assertTrue("slope std err not NaN", Double.isNaN(regression.getSlopeStdErr()));
        assertTrue("intercept std err not NaN", Double.isNaN(regression.getInterceptStdErr()));
        assertTrue("MSE not NaN", Double.isNaN(regression.getMeanSquareError()));
        assertTrue("e not NaN", Double.isNaN(regression.getR()));
        assertTrue("r-square not NaN", Double.isNaN(regression.getRSquare()));
        assertTrue( "RSS not NaN", Double.isNaN(regression.getRegressionSumSquares()));
        assertTrue("SSE not NaN",Double.isNaN(regression.getSumSquaredErrors()));
        assertTrue("SSTO not NaN", Double.isNaN(regression.getTotalSumSquares()));
        assertTrue("predict not NaN", Double.isNaN(regression.predict(0)));

        regression.addData(1, 2);
        regression.addData(1, 3);

        // No x variation, so these should still blow...
        assertTrue("intercept not NaN", Double.isNaN(regression.getIntercept()));
        assertTrue("slope not NaN", Double.isNaN(regression.getSlope()));
        assertTrue("slope std err not NaN", Double.isNaN(regression.getSlopeStdErr()));
        assertTrue("intercept std err not NaN", Double.isNaN(regression.getInterceptStdErr()));
        assertTrue("MSE not NaN", Double.isNaN(regression.getMeanSquareError()));
        assertTrue("e not NaN", Double.isNaN(regression.getR()));
        assertTrue("r-square not NaN", Double.isNaN(regression.getRSquare()));
        assertTrue("RSS not NaN", Double.isNaN(regression.getRegressionSumSquares()));
        assertTrue("SSE not NaN", Double.isNaN(regression.getSumSquaredErrors()));
        assertTrue("predict not NaN", Double.isNaN(regression.predict(0)));

        // but SSTO should be OK
        assertTrue("SSTO NaN", !Double.isNaN(regression.getTotalSumSquares()));

        regression = new SimpleRegression();

        regression.addData(1, 2);
        regression.addData(3, 3);

        // All should be OK except MSE, s(b0), s(b1) which need one more df 
        assertTrue("interceptNaN", !Double.isNaN(regression.getIntercept()));
        assertTrue("slope NaN", !Double.isNaN(regression.getSlope()));
        assertTrue ("slope std err not NaN", Double.isNaN(regression.getSlopeStdErr()));
        assertTrue("intercept std err not NaN", Double.isNaN(regression.getInterceptStdErr()));
        assertTrue("MSE not NaN", Double.isNaN(regression.getMeanSquareError()));
        assertTrue("r NaN", !Double.isNaN(regression.getR()));
        assertTrue("r-square NaN", !Double.isNaN(regression.getRSquare()));
        assertTrue("RSS NaN", !Double.isNaN(regression.getRegressionSumSquares()));
        assertTrue("SSE NaN", !Double.isNaN(regression.getSumSquaredErrors()));
        assertTrue("SSTO NaN", !Double.isNaN(regression.getTotalSumSquares()));
        assertTrue("predict NaN", !Double.isNaN(regression.predict(0)));

        regression.addData(1, 4);

        // MSE, MSE, s(b0), s(b1) should all be OK now
        assertTrue("MSE NaN", !Double.isNaN(regression.getMeanSquareError()));
        assertTrue("slope std err NaN", !Double.isNaN(regression.getSlopeStdErr()));
        assertTrue("intercept std err NaN", !Double.isNaN(regression.getInterceptStdErr()));
    }

    public void testClear() {
        SimpleRegression regression = new SimpleRegression();
        regression.addData(corrData);
        assertEquals("number of observations", 17, regression.getN());
        regression.clear();
        assertEquals("number of observations", 0, regression.getN());
        regression.addData(corrData);
        assertEquals("r-square", .896123, regression.getRSquare(), 10E-6);
        regression.addData(data);
        assertEquals("number of observations", 53, regression.getN());
    }

    public void testInference() throws Exception {
        //----------  verified against R, version 1.8.1 -----
        // infData
        SimpleRegression regression = new SimpleRegression();
        regression.addData(infData);
        assertEquals("slope std err", 0.011448491,
                regression.getSlopeStdErr(), 1E-10);
        assertEquals("std err intercept", 0.286036932,
                regression.getInterceptStdErr(),1E-8);
        assertEquals("significance", 4.596e-07,
                regression.getSignificance(),1E-8);    
        assertEquals("slope conf interval half-width", 0.0270713794287, 
                regression.getSlopeConfidenceInterval(),1E-8);
        // infData2
        regression = new SimpleRegression();
        regression.addData(infData2);
        assertEquals("slope std err", 1.07260253,
                regression.getSlopeStdErr(), 1E-8);
        assertEquals("std err intercept",4.17718672,
                regression.getInterceptStdErr(),1E-8);
        assertEquals("significance", 0.261829133982,
                regression.getSignificance(),1E-11);    
        assertEquals("slope conf interval half-width", 2.97802204827, 
                regression.getSlopeConfidenceInterval(),1E-8);
        //------------- End R-verified tests -------------------------------
        
        //FIXME: get a real example to test against with alpha = .01
        assertTrue("tighter means wider",
                regression.getSlopeConfidenceInterval() < regression.getSlopeConfidenceInterval(0.01));
     
        try {
            double x = regression.getSlopeConfidenceInterval(1);
            fail("expecting IllegalArgumentException for alpha = 1");
        } catch (IllegalArgumentException ex) {
            ;
        }  

    }

    public void testPerfect() throws Exception {
        SimpleRegression regression = new SimpleRegression();
        int n = 100;
        for (int i = 0; i < n; i++) {
            regression.addData(((double) i) / (n - 1), i);
        }
        assertEquals(0.0, regression.getSignificance(), 1.0e-5);
        assertTrue(regression.getSlope() > 0.0);
    }

    public void testPerfectNegative() throws Exception {
        SimpleRegression regression = new SimpleRegression();
        int n = 100;
        for (int i = 0; i < n; i++) {
            regression.addData(- ((double) i) / (n - 1), i);
        }
   
        assertEquals(0.0, regression.getSignificance(), 1.0e-5);
        assertTrue(regression.getSlope() < 0.0);   
    }

    public void testRandom() throws Exception {
        SimpleRegression regression = new SimpleRegression();
        Random random = new Random(1);
        int n = 100;
        for (int i = 0; i < n; i++) {
            regression.addData(((double) i) / (n - 1), random.nextDouble());
        }

        assertTrue( 0.0 < regression.getSignificance()
                    && regression.getSignificance() < 1.0);       
    }
}