Package org.opensourcephysics.numerics

Class FFTReal

java.lang.Object
org.opensourcephysics.numerics.FFTReal
public class FFTReal extends Object
FFTReal computes the discrete Fourier coefficients a[0], ...., a[N/2] and b[1], ...., b[N/2 - 1] of the discrete partial Fourier sum a[0] + a[1]*cos(N/2*omega*x) + Sum (k=1,2,...,N/2-1) (a[2*k] * cos(k * omega * x) + a[2*k+1] * sin(k * omega * x)) given real functional values y[0], ...., y[N-1]. Adapted by W. Christian for use in the OSP project.
Version:
1.0
Author:
Bruce R. Miller bruce.miller@nist.gov, Contribution of the National Institute of Standards and Technology,, Derived from GSL (Gnu Scientific Library), GSL's FFT Code by Brian Gough bjg@vvv.lanl.gov, Since GSL is released under, GPL,, this class must also be.

  • Constructor Summary

    Constructors
    Constructor
    Description
    FFTReal()
    Constructs a real FFT transformation for n data points.
    FFTReal(int n)
    Constructs a real FFT transformation for n data points.

  • Method Summary

    Modifier and Type
    Method
    Description
    double[]
    backtransform(double[] data)
    Computes the (unnomalized) inverse FFT of data, leaving it in place.
    int
    getN()
    Gets the number of data points.
    double[]
    getNaturalFreq(double delta)
    Gets an array containing the frequencies in natural order.
    double[]
    getNaturalFreq(double xmin, double xmax)
    Gets an array containing the frequencies in natural order.
    double[]
    getNaturalOmega(double delta)
    Gets an array containing the frequencies in natural order.
    double[]
    getNaturalOmega(double xmin, double xmax)
    Gets an array containing the frequencies in natural order.
    double[]
    inverse(double[] data)
    Computes the (nomalized) inverse FFT of data, leaving it in place.
    void
    setN(int n)
    Sets the number of data points.
    double[]
    transform(double[] data)
    Computes the Fast Fourier Transform of the data leaving the result in data.

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • FFTReal

      public FFTReal()
      Constructs a real FFT transformation for n data points.

    • FFTReal

      public FFTReal(int n)
      Constructs a real FFT transformation for n data points.
      Parameters:
      n - the number of data points

  • Method Details

    • setN

      public void setN(int n)
      Sets the number of data points.
      Parameters:
      n - int

    • getN

      public int getN()
      Gets the number of data points.
      Returns:
      int

    • transform

      public double[] transform(double[] data)
      Computes the Fast Fourier Transform of the data leaving the result in data. The given array is returned after it has been transformed.
      Parameters:
      data - double[] the data to be transformed
      Returns:
      double[] the data after the FFT

    • backtransform

      public double[] backtransform(double[] data)
      Computes the (unnomalized) inverse FFT of data, leaving it in place. The given array is returned after it has been transformed.
      Parameters:
      data - double[] the data to be transformed
      Returns:
      double[] the data after the FFT

    • inverse

      public double[] inverse(double[] data)
      Computes the (nomalized) inverse FFT of data, leaving it in place. The given array is returned after it has been transformed.
      Parameters:
      data - double[] the data to be transformed
      Returns:
      double[] the data after the FFT

    • getNaturalFreq

      public double[] getNaturalFreq(double delta)
      Gets an array containing the frequencies in natural order. Data are separated by delta.
      Parameters:
      delta -
      Returns:
      the array of frequencies

    • getNaturalFreq

      public double[] getNaturalFreq(double xmin, double xmax)
      Gets an array containing the frequencies in natural order. The first data point is at xmin (tmin) and the last data point is at xmax (tmax).
      Parameters:
      xmin -
      xmax -
      Returns:
      the array of frequencies

    • getNaturalOmega

      public double[] getNaturalOmega(double delta)
      Gets an array containing the frequencies in natural order. Data are separated by delta.
      Parameters:
      delta -
      Returns:
      the array of frequencies

    • getNaturalOmega

      public double[] getNaturalOmega(double xmin, double xmax)
      Gets an array containing the frequencies in natural order. The first data point is at xmin (tmin) and the last data point is at xmax (tmax).
      Parameters:
      xmin -
      xmax -
      Returns:
      the array of frequencies