Package smile.util.function

Interface Function

All Superinterfaces:
Serializable
All Known Subinterfaces:
DifferentiableFunction, DotProductKernel, IsotropicKernel, RadialBasisFunction, Variogram
All Known Implementing Classes:
BinarySparseGaussianKernel, BinarySparseHyperbolicTangentKernel, BinarySparseLaplacianKernel, BinarySparseLinearKernel, BinarySparseMaternKernel, BinarySparsePolynomialKernel, BinarySparseThinPlateSplineKernel, Exp, ExponentialVariogram, Gaussian, GaussianKernel, GaussianRadialBasis, GaussianVariogram, HyperbolicTangent, HyperbolicTangentKernel, InverseMultiquadricRadialBasis, Kurtosis, Laplacian, LaplacianKernel, LinearKernel, LogCosh, Matern, MaternKernel, MultiquadricRadialBasis, Polynomial, PolynomialKernel, PowerVariogram, Scaler, SparseGaussianKernel, SparseHyperbolicTangentKernel, SparseLaplacianKernel, SparseLinearKernel, SparseMaternKernel, SparsePolynomialKernel, SparseThinPlateSplineKernel, SphericalVariogram, ThinPlateRadialBasis, ThinPlateSpline, ThinPlateSplineKernel
public interface Function extends Serializable
An interface representing a univariate real function.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final org.slf4j.Logger
    logger
    Logging facility.

  • Method Summary

    Modifier and Type
    Method
    Description
    default double
    apply(double x)
    Computes the value of the function at x.
    double
    f(double x)
    Computes the value of the function at x.
    default double
    inv(double x)
    Computes the value of the inverse function at x.
    default double
    root(double x1, double x2, double tol, int maxIter)
    Brent's method for root-finding.

  • Field Details

    • logger

      static final org.slf4j.Logger logger
      Logging facility.

  • Method Details

    • f

      double f(double x)
      Computes the value of the function at x.
      Parameters:
      x - a real number.
      Returns:
      the function value.

    • inv

      default double inv(double x)
      Computes the value of the inverse function at x.
      Parameters:
      x - a real number.
      Returns:
      the inverse function value.

    • apply

      default double apply(double x)
      Computes the value of the function at x. It delegates the computation to f(). This is simply for Scala convenience.
      Parameters:
      x - a real number.
      Returns:
      the function value.

    • root

      default double root(double x1, double x2, double tol, int maxIter)
      Brent's method for root-finding. It combines the bisection method, the secant method and inverse quadratic interpolation. It has the reliability of bisection, but it can be as quick as some of the less-reliable methods. The algorithm tries to use the potentially fast-converging secant method or inverse quadratic interpolation if possible, but it falls back to the more robust bisection method if necessary.

      The method is guaranteed to converge as long as the function can be evaluated within the initial interval known to contain a root.

      Parameters:
      x1 - the left end of search interval.
      x2 - the right end of search interval.
      tol - the desired accuracy (convergence tolerance).
      maxIter - the maximum number of iterations.
      Returns:
      the root.