Example usage for org.apache.commons.math3.analysis.polynomials PolynomialSplineFunction PolynomialSplineFunction

Introduction

In this page you can find the example usage for org.apache.commons.math3.analysis.polynomials PolynomialSplineFunction PolynomialSplineFunction.

Prototype

public PolynomialSplineFunction(double knots[], PolynomialFunction polynomials[]) 

Source Link

Document

Construct a polynomial spline function with the given segment delimiters and interpolating polynomials.

Usage

From source file:au.gov.ga.conn4d.utils.SplineInterpolator.java

/**
 * Computes an interpolating function for the data set.
 * //  www.  j  a v  a  2  s  . c  om
 * @param x
 *            the arguments for the interpolation points
 * @param y
 *            the values for the interpolation points
 * @return a function which interpolates the data set
 * @throws DimensionMismatchException
 *             if {@code x} and {@code y} have different sizes.
 * @throws NonMonotonicSequenceException
 *             if {@code x} is not sorted in strict increasing order.
 * @throws NumberIsTooSmallException
 *             if the size of {@code x} is smaller than 3.
 */
public PolynomialSplineFunction interpolate(double x[], double y[])
        throws DimensionMismatchException, NumberIsTooSmallException, NonMonotonicSequenceException {
    if (x.length != y.length) {
        throw new DimensionMismatchException(x.length, y.length);
    }

    if (x.length < 3) {
        throw new NumberIsTooSmallException(LocalizedFormats.NUMBER_OF_POINTS, x.length, 3, true);
    }

    // Number of intervals. The number of data points is n + 1.
    final int n = x.length - 1;

    MathArrays.checkOrder(x);

    // Differences between knot points
    final double h[] = new double[n];
    for (int i = 0; i < n; i++) {
        h[i] = x[i + 1] - x[i];
    }

    final double mu[] = new double[n];
    final double z[] = new double[n + 1];
    mu[0] = 0d;
    z[0] = 0d;
    double g = 0;
    for (int i = 1; i < n; i++) {
        g = 2d * (x[i + 1] - x[i - 1]) - h[i - 1] * mu[i - 1];
        mu[i] = h[i] / g;
        z[i] = (3d * (y[i + 1] * h[i - 1] - y[i] * (x[i + 1] - x[i - 1]) + y[i - 1] * h[i]) / (h[i - 1] * h[i])
                - h[i - 1] * z[i - 1]) / g;
    }

    // cubic spline coefficients -- b is linear, c quadratic, d is cubic
    // (original y's are constants)
    final double b[] = new double[n];
    final double c[] = new double[n + 1];
    final double d[] = new double[n];

    z[n] = 0d;
    c[n] = 0d;

    for (int j = n - 1; j >= 0; j--) {
        c[j] = z[j] - mu[j] * c[j + 1];
        b[j] = (y[j + 1] - y[j]) / h[j] - h[j] * (c[j + 1] + 2d * c[j]) / 3d;
        d[j] = (c[j + 1] - c[j]) / (3d * h[j]);
    }

    final PolynomialFunction polynomials[] = new PolynomialFunction[n];
    final double coefficients[] = new double[4];
    for (int i = 0; i < n; i++) {
        coefficients[0] = y[i];
        coefficients[1] = b[i];
        coefficients[2] = c[i];
        coefficients[3] = d[i];
        polynomials[i] = new PolynomialFunction(coefficients);
    }

    return new PolynomialSplineFunction(x, polynomials);
}

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From source file:au.gov.ga.conn4d.utils.SplineInterpolator.java

public PolynomialSplineFunction interpolate(double x[], float y[])
        throws DimensionMismatchException, NumberIsTooSmallException, NonMonotonicSequenceException {
    if (x.length != y.length) {
        throw new DimensionMismatchException(x.length, y.length);
    }// w  w  w.j av  a2  s .c  o m

    if (x.length < 3) {
        throw new NumberIsTooSmallException(LocalizedFormats.NUMBER_OF_POINTS, x.length, 3, true);
    }

    // Number of intervals. The number of data points is n + 1.
    final int n = x.length - 1;

    MathArrays.checkOrder(x);

    // Differences between knot points
    final double h[] = new double[n];
    for (int i = 0; i < n; i++) {
        h[i] = x[i + 1] - x[i];
    }

    final double mu[] = new double[n];
    final double z[] = new double[n + 1];
    mu[0] = 0d;
    z[0] = 0d;
    double g = 0;
    for (int i = 1; i < n; i++) {
        g = 2d * (x[i + 1] - x[i - 1]) - h[i - 1] * mu[i - 1];
        mu[i] = h[i] / g;
        z[i] = (3d * (y[i + 1] * h[i - 1] - y[i] * (x[i + 1] - x[i - 1]) + y[i - 1] * h[i]) / (h[i - 1] * h[i])
                - h[i - 1] * z[i - 1]) / g;
    }

    // cubic spline coefficients -- b is linear, c quadratic, d is cubic
    // (original y's are constants)
    final double b[] = new double[n];
    final double c[] = new double[n + 1];
    final double d[] = new double[n];

    z[n] = 0d;
    c[n] = 0d;

    for (int j = n - 1; j >= 0; j--) {
        c[j] = z[j] - mu[j] * c[j + 1];
        b[j] = (y[j + 1] - y[j]) / h[j] - h[j] * (c[j + 1] + 2d * c[j]) / 3d;
        d[j] = (c[j + 1] - c[j]) / (3d * h[j]);
    }

    final PolynomialFunction polynomials[] = new PolynomialFunction[n];
    final double coefficients[] = new double[4];
    for (int i = 0; i < n; i++) {
        coefficients[0] = y[i];
        coefficients[1] = b[i];
        coefficients[2] = c[i];
        coefficients[3] = d[i];
        polynomials[i] = new PolynomialFunction(coefficients);
    }

    return new PolynomialSplineFunction(x, polynomials);
}

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