com.actelion.research.util.FastSpline Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of openchemlib Show documentation
Show all versions of openchemlib Show documentation
Open Source Chemistry Library
/*
* Copyright (c) 1997 - 2016
* Actelion Pharmaceuticals Ltd.
* Gewerbestrasse 16
* CH-4123 Allschwil, Switzerland
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. Neither the name of the the copyright holder nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
package com.actelion.research.util;
import java.util.*;
/**
* Represents a polynomial spline function.
*/
public final class FastSpline {
public final static class Polynome {
private final double coeffs[]; //x0 x1 x2 x3
public Polynome(double[] coeffs) {
this.coeffs = coeffs;
}
public final Polynome derivative() {
return new Polynome(new double[] {coeffs[1], 2*coeffs[2], 3*coeffs[3], 0});
}
public final double value(double x) {
return coeffs[0]+x*(coeffs[1]+x*(coeffs[2]+x*coeffs[3]));
}
public final double[] getCoefficients() {
return coeffs;
}
}
/** Spline segment interval delimiters (knots). Size is n+1 for n segments. */
private final double knots[];
/**
* The polynomial functions that make up the spline. The first element
* determines the value of the spline over the first subinterval, the
* second over the second, etc. Spline function values are determined by
* evaluating these functions at (x - knot[i]) where i is the
* knot segment to which x belongs.
*/
private final Polynome polynomials[];
/**
* Number of spline segments = number of polynomials
* = number of partition points - 1
*/
private final int n;
/**
* Construct a polynomial spline function with the given segment delimiters
* and interpolating polynomials.
*/
public FastSpline(double knots[], Polynome polynomials[]) {
this.n = knots.length -1;
this.knots = new double[n + 1];
this.polynomials = new Polynome[n];
System.arraycopy(knots, 0, this.knots, 0, n + 1);
System.arraycopy(polynomials, 0, this.polynomials, 0, n);
}
/**
* Compute the value for the function.
*/
public final double value(double v) throws ArrayIndexOutOfBoundsException {
int i = Arrays.binarySearch(knots, v);
if (i < 0) i = -i - 2;
if (i < 0) i = 0;
return polynomials[i].value(v - knots[i]);
}
/**
* Returns the derivative of the polynomial spline function as a PolynomialSplineFunction
*/
public final FastSpline derivative() {
Polynome derivativePolynomials[] = new Polynome[n];
for (int i = 0; i < n; i++) derivativePolynomials[i] = polynomials[i].derivative();
return new FastSpline(knots, derivativePolynomials);
}
}