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/*
* Copyright (c) 2009-2017, Peter Abeles. All Rights Reserved.
*
* This file is part of Efficient Java Matrix Library (EJML).
*
* 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.ejml.example;
import org.ejml.UtilEjml;
import org.junit.Test;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
/**
* @author Peter Abeles
*/
public class TestPolynomialFit {
/**
* Test with perfect data
*/
@Test
public void testPerfect() {
double coef[] = new double[]{1,-2,3};
double x[] = new double[]{-2,1,0.5,2,3,4,5,7,8,9.2,10.2,4.3,6.7};
double y[] = new double[ x.length ];
for( int i = 0; i < y.length; i++ ) {
double v = 0;
double xx = 1;
for (double c : coef) {
v += c * xx;
xx *= x[i];
}
y[i] = v;
}
PolynomialFit alg = new PolynomialFit(2);
alg.fit(x,y);
double found[] = alg.getCoef();
for( int i = 0; i < coef.length; i++ ) {
assertEquals(coef[i],found[i], UtilEjml.TEST_F64);
}
}
/**
* Make one of the observations way off and see if it is removed
*/
@Test
public void testNoise() {
double coef[] = new double[]{1,-2,3};
double x[] = new double[]{-2,1,0.5,2,3,4,5,7,8,9.2,10.2,4.3,6.7};
double y[] = new double[ x.length ];
for( int i = 0; i < y.length; i++ ) {
double v = 0;
double xx = 1;
for (double c : coef) {
v += c * xx;
xx *= x[i];
}
y[i] = v;
}
y[4] += 3.5;
PolynomialFit alg = new PolynomialFit(2);
alg.fit(x,y);
double found[] = alg.getCoef();
// the coefficients that it initialy computes should be incorrect
for( int i = 0; i < coef.length; i++ ) {
assertTrue(Math.abs(coef[i]-found[i])>UtilEjml.TEST_F64);
}
//remove the outlier
alg.removeWorstFit();
// now see if the solution is perfect
found = alg.getCoef();
for( int i = 0; i < coef.length; i++ ) {
assertEquals(coef[i],found[i],UtilEjml.TEST_F64);
}
}
}
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