/* ===========================================================
* JFreeChart : a free chart library for the Java(tm) platform
* ===========================================================
*
* (C) Copyright 2000-2011, by Object Refinery Limited and Contributors.
*
* Project Info: http://www.jfree.org/jfreechart/index.html
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
* USA.
*
* [Oracle and Java are registered trademarks of Oracle and/or its affiliates.
* Other names may be trademarks of their respective owners.]
*
* -------------------------
* PolynomialFunction2D.java
* -------------------------
* (C) Copyright 2009, by Object Refinery Limited.
*
* Original Author: Peter Kolb;
* Contributor(s): David Gilbert (for Object Refinery Limited);
*
* Changes:
* --------
* 23-Mar-2009 : Version 1, patch 2795746 (PK);
* 28-May-2009 : Integrated in JFreeChart with modifications (DG);
*
*/
package org.jfree.data.function;
import java.io.Serializable;
import java.util.Arrays;
import org.jfree.chart.HashUtilities;
/**
* A function in the form <code>y = a0 + a1 * x + a2 * x^2 + ... + an *
* x^n</code>. Instances of this class are immutable.
*
* @since 1.0.14
*/
public class PolynomialFunction2D implements Function2D, Serializable {
/** The coefficients. */
private double[] coefficients;
/**
* Constructs a new polynomial function <code>y = a0 + a1 * x + a2 * x^2 +
* ... + an * x^n</code>
*
* @param coefficients an array with the coefficients [a0, a1, ..., an]
* (<code>null</code> not permitted).
*/
public PolynomialFunction2D(double[] coefficients) {
if (coefficients == null) {
throw new IllegalArgumentException("Null 'coefficients' argument");
}
this.coefficients = (double[]) coefficients.clone();
}
/**
* Returns a copy of the coefficients array that was specified in the
* constructor.
*
* @return The coefficients array.
*/
public double[] getCoefficients() {
return (double[]) this.coefficients.clone();
}
/**
* Returns the order of the polynomial.
*
* @return The order.
*/
public int getOrder() {
return this.coefficients.length - 1;
}
/**
* Returns the function value.
*
* @param x the x-value.
*
* @return The value.
*/
public double getValue(double x) {
double y = 0;
for(int i = 0; i < coefficients.length; i++){
y += coefficients[i] * Math.pow(x, i);
}
return y;
}
/**
* Tests this function for equality with an arbitrary object.
*
* @param obj the object (<code>null</code> permitted).
*
* @return A boolean.
*/
public boolean equals(Object obj) {
if (!(obj instanceof PolynomialFunction2D)) {
return false;
}
PolynomialFunction2D that = (PolynomialFunction2D) obj;
return Arrays.equals(this.coefficients, that.coefficients);
}
/**
* Returns a hash code for this instance.
*
* @return A hash code.
*/
public int hashCode() {
return HashUtilities.hashCodeForDoubleArray(this.coefficients);
}
}
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