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From "Daren Drummond (JIRA)" <j...@apache.org>
Subject [jira] Created: (MATH-303) CurveFitter.fit(ParametricRealFunction, double[]) used with LevenbergMarquardtOptimizer throws ArrayIndexOutOfBoundsException when double[] length > 1 (AbstractLeastSquaresOptimizer.java:187)
Date Mon, 19 Oct 2009 21:20:59 GMT
```CurveFitter.fit(ParametricRealFunction, double[]) used with LevenbergMarquardtOptimizer throws
ArrayIndexOutOfBoundsException when double[] length > 1 (AbstractLeastSquaresOptimizer.java:187)
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Key: MATH-303
URL: https://issues.apache.org/jira/browse/MATH-303
Project: Commons Math
Issue Type: Bug
Affects Versions: 2.0
Environment: Java, Linux Ubuntu 9.04
Reporter: Daren Drummond

CurveFitter.fit(ParametricRealFunction, double[]) throws ArrayIndexOutOfBoundsException at
AbstractLeastSquaresOptimizer.java:187 when used with the  LevenbergMarquardtOptimizer  and
the length of the initial guess array is greater than 1.  The code will run if the initialGuess
array is of length 1, but then CurveFitter.fit() just returns the same value as the initialGuess
array (I'll file this as a separate issue).  Here is my example code:

LevenbergMarquardtOptimizer optimizer = new LevenbergMarquardtOptimizer();
CurveFitter fitter = new CurveFitter(optimizer);
SimpleInverseFunction sif = new SimpleInverseFunction(); // Class provided below
double[] initialguess = new double[2];
initialguess[0] = 1.0d;
initialguess[1] = .5d;
double[] bestCoefficients = fitter.fit(sif, initialguess); // <---- throws exception
here

/**
* This is my implementation of ParametricRealFunction
* Implements y = ax^-1 + b for use with an Apache CurveFitter implementation
*/
private class SimpleInverseFunction implements ParametricRealFunction
{
public double value(double x, double[] doubles) throws FunctionEvaluationException
{
//y = ax^-1 + b
//"double[] must include at least 1 but not more than 2 coefficients."
if(doubles == null || doubles.length ==0 || doubles.length > 2) throw new FunctionEvaluationException(doubles);
double a = doubles[0];
double b = 0;
if(doubles.length >= 2) b = doubles[1];
return a * Math.pow(x, -1d) + b;
}
public double[] gradient(double x, double[] doubles) throws FunctionEvaluationException
{
//derivative: -ax^-2
//"double[] must include at least 1 but not more than 2 coefficients."
if(doubles == null || doubles.length ==0 || doubles.length > 2) throw new FunctionEvaluationException(doubles);
double a = doubles[0];
double b = 0;
if(doubles.length >= 2) b = doubles[1];
double derivative = -a * Math.pow(x, -2d);
}
}

This is the resulting stack trace:

java.lang.ArrayIndexOutOfBoundsException: 1
at org.apache.commons.math.optimization.general.AbstractLeastSquaresOptimizer.updateJacobian(AbstractLeastSquaresOptimizer.java:187)
at org.apache.commons.math.optimization.general.LevenbergMarquardtOptimizer.doOptimize(LevenbergMarquardtOptimizer.java:241)
at org.apache.commons.math.optimization.general.AbstractLeastSquaresOptimizer.optimize(AbstractLeastSquaresOptimizer.java:346)
at org.apache.commons.math.optimization.fitting.CurveFitter.fit(CurveFitter.java:134)