org.apache.commons.math3.analysis.interpolation

## Class HermiteInterpolator

- java.lang.Object
- - org.apache.commons.math3.analysis.interpolation.HermiteInterpolator

- All Implemented Interfaces:
    UnivariateDifferentiableVectorFunction, UnivariateVectorFunction

      public class HermiteInterpolator
      extends Object
      implements UnivariateDifferentiableVectorFunction

  Polynomial interpolator using both sample values and sample derivatives.

  The interpolation polynomials match all sample points, including both values and provided derivatives. There is one polynomial for each component of the values vector. All polynomials have the same degree. The degree of the polynomials depends on the number of points and number of derivatives at each point. For example the interpolation polynomials for n sample points without any derivatives all have degree n-1. The interpolation polynomials for n sample points with the two extreme points having value and first derivative and the remaining points having value only all have degree n+1. The interpolation polynomial for n sample points with value, first and second derivative for all points all have degree 3n-1.

  Since:
    3.1

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `HermiteInterpolator()` Create an empty interpolator.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `addSamplePoint(double x, double[]... value)` Add a sample point.
    `PolynomialFunction[]` | `getPolynomials()` Compute the interpolation polynomials.
    `DerivativeStructure[]` | `value(DerivativeStructure x)` Interpolate value at a specified abscissa.
    `double[]` | `value(double x)` Interpolate value at a specified abscissa.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### HermiteInterpolator

          public HermiteInterpolator()

      Create an empty interpolator.

  - ### Method Detail

    - #### addSamplePoint

          public void addSamplePoint(double x,
                            double[]... value)
                              throws ZeroException,
                                     MathArithmeticException

      Add a sample point.

      This method must be called once for each sample point. It is allowed to mix some calls with values only with calls with values and first derivatives.

      The point abscissae for all calls must be different.

      Parameters:
        `x` - abscissa of the sample point
        `value` - value and derivatives of the sample point (if only one row is passed, it is the value, if two rows are passed the first one is the value and the second the derivative and so on)
      Throws:
        `ZeroException` - if the abscissa difference between added point and a previous point is zero (i.e. the two points are at same abscissa)
        `MathArithmeticException` - if the number of derivatives is larger than 20, which prevents computation of a factorial

    - #### getPolynomials

          public PolynomialFunction[] getPolynomials()
                                              throws NoDataException

      Compute the interpolation polynomials.
      Returns:
        interpolation polynomials array
      Throws:
        `NoDataException` - if sample is empty

    - #### value

          public double[] value(double x)
                         throws NoDataException

      Interpolate value at a specified abscissa.

      Calling this method is equivalent to call the `value` methods of all polynomials returned by `getPolynomials`, except it does not build the intermediate polynomials, so this method is faster and numerically more stable.

      Specified by:
        `value` in interface `UnivariateVectorFunction`
      Parameters:
        `x` - interpolation abscissa
      Returns:
        interpolated value
      Throws:
        `NoDataException` - if sample is empty

    - #### value

          public DerivativeStructure[] value(DerivativeStructure x)
                                      throws NoDataException

      Interpolate value at a specified abscissa.

      Calling this method is equivalent to call the `value` methods of all polynomials returned by `getPolynomials`, except it does not build the intermediate polynomials, so this method is faster and numerically more stable.

      Specified by:
        `value` in interface `UnivariateDifferentiableVectorFunction`
      Parameters:
        `x` - interpolation abscissa
      Returns:
        interpolated value
      Throws:
        `NoDataException` - if sample is empty

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