Luc
Thanks for your comments. I have taken the 2DCurveExponentialX as a first
attempt here. The basic equation is y = a + b*e^(c*x) (is the math e, natural
exponential function). I have written the following implementation of the of
the ParametricRealFunction for this, see below. Not having any experience with
this type a implementation I did the best I could. However, I am getting this
exception:
org.apache.commons.math.optimization.OptimizationException: unable to compute
covariances: singular problem
I unfortunately do not have any idea what this means or how to remedy it. Your
help is appreciated
Thanks
Roger
/**
* implementation of ParametricRealFunction clase for
* y = a + be^(cx)
*/
public static class TwoDCurveNaturalLogX implements ParametricRealFunction
{
/*
*"double[] coeffs = must include at least 1 but not more than 3
coefficients."
*/
@Override
public double value(double x, double[] coeffs) throws
FunctionEvaluationException
{
if(coeffs == null || coeffs.length == 0 || coeffs.length > 3)
{
if (coeffs != null)
{
for (int ii=0; ii < coeffs.length; ii++)
{
//System.out.println("\t coeffs ["+ii+"]"+coeffs[ii]);
}
}
else
{
//System.out.println("No coeffs were passed in");
}
throw new FunctionEvaluationException(coeffs);
}
double a = coeffs[0];
double b = 0;
double c = 0;
if(coeffs.length >= 2)
b = coeffs[1];
if(coeffs.length >= 3)
c = coeffs[2];
double value = a + b*Math.pow(Math.E, (c*x));
//System.out.println("\t value ["+value+"]");
return value;
}
/*
* derivative: y = b*c*e^(c*x)
* double[] coeffs = must include at least 1 but not more than 3
coefficients."
*/
@Override
public double[] gradient(double x, double[] coeffs) throws
FunctionEvaluationException {
if(coeffs == null || coeffs.length ==0 || coeffs.length > 3)
{
throw new FunctionEvaluationException(coeffs);
}
System.out.println("\t coeffs length = ["+coeffs.length+"]");
double a = coeffs[0];
double b = 0;
double c = 0;
if(coeffs.length >= 2)
b = coeffs[1];
if(coeffs.length >= 3)
c = coeffs[2];
double gradient = b*c*Math.pow(Math.E, (c*x));
double[] gradientVector = new double[3];
gradientVector[0] = gradient;
gradientVector[1] = 0;
gradientVector[2] = 0;
System.out.println("\t gradient ["+gradient+"]");
return gradientVector;
}
}
Luc
________________________________
From: [email protected]
Sent: Thursday, January 21, 2010 11:46 AM
To: [email protected]
Subject: [MATH] Need help on math libraries for curve generation
We are evaluating the apache math library
(http://commons.apache.org/math/index.html) for use on one of projects. In this
project we need to generate curves based on the following functions:
2DCurve3rdOrderXPolynomial
2DCurveExponentialX
2DCurveNaturalLogX
2DCurveSquareRootX
2DCurveTimeConstantX
2DCurveExponentialDecayX
2DCurveLogarithmicDecayX
3DCurve4thOrderXPolynomial
3DCurveExponentialX
3DCurveNaturalLogX
3DCurveSquareRootX
3DCurveTimeConstantX
3DCurve3rdOrderZTimes4thOrderX
3DCurveExponentialDecayX
3DCurveLogarithmicDecayX
3DCurveExponentialDecayZ
3DCurveLogarithmicDecayZ
3DCurveHyprebolicDecayX
For each function generated from data we also need:
Coefficient of Determination
Sum of Squares
Standard Error of Regression
Does anyone have experience with this library to direct us to which classes can
be used to handle these requirements?
Thanks
Roger Ball
