Package org.opensourcephysics.numerics

Class FFT2D

java.lang.Object
org.opensourcephysics.numerics.FFT2D
public class FFT2D extends Object
FFT2D computes the FFT of 2 dimensional complex, double precision data. This class has been copied from Bruce Miller's FFT package for use in the Open Source Physics Project. The original package contains code for other transformations and other data types. The data is stored in a 1-dimensional array in Row-Major order. The physical layout in the array data, of the mathematical data d[i,j] is as follows: 
    Re(d[i,j]) = data[i*rowspan + 2*j]
    Im(d[i,j]) = data[i*rowspan + 2*j + 1]
where rowspan must be at least 2*ncols (it defaults to 2*ncols). The transformed data is returned in the original data array in wrap-around order along each dimension.
Author:
Bruce R. Miller bruce.miller@nist.gov, Contribution of the National Institute of Standards and Technology,, not subject to copyright.

  • Constructor Summary

    Constructors
    Constructor
    Description
    FFT2D(int nrows, int ncols)
    Create an FFT for transforming nrows*ncols points of Complex, double precision data.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    backtransform(double[] data)
    Compute the (unnomalized) inverse FFT of data, leaving it in place.
    protected void
    checkData(double[] data, int rowspan)
     
    double
    getFreqMax(double min, double max, int n)
    Gets the maximum frequency given the domain and the number of points.
    double
    getFreqMin(double min, double max, int n)
    Gets the minimum frequency given the domain and the number of points.
    double[]
    getNaturalFreqX(double delta)
    Gets an array containing the frequencies in natural order.
    double[]
    getNaturalFreqX(double xmin, double xmax)
    Gets an array containing the frequencies in natural order.
    double[]
    getNaturalFreqY(double delta)
    Gets an array containing the frequencies in natural order if samples in the orginal data are separated by delta in y.
    double[]
    getNaturalFreqY(double ymin, double ymax)
    Gets an array containing the frequencies in natural order.
    double[]
    getNaturalModes(int n)
    Gets an array containing the mode numbers in natural order.
    double[]
    getNaturalOmegaX(double delta)
    Gets an array containing the angular frequencies (wavenumbers) in natural order.
    double[]
    getNaturalOmegaX(double xmin, double xmax)
    Gets an array containing the angular frequencies (wavenumbers) in natural order.
    double[]
    getNaturalOmegaY(double delta)
    Gets an array containing the frequencies in natural order if samples in the orginal data are separated by delta in y.
    double[]
    getNaturalOmegaY(double ymin, double ymax)
    Gets an array containing the frequencies in natural order.
    double[]
    getWrappedFreq(double delta, int n)
    Gets an array containing the frequencies in wrap-around order.
    double[]
    getWrappedModes(int n)
    Gets an array containing the mode numbers in wrap-around order.
    double[]
    getWrappedOmegaX(double xmin, double xmax)
    Gets an array containing the angular frequencies (wavenumbers) in natural order.
    double[]
    getWrappedOmegaY(double ymin, double ymax)
    Gets an array containing the angular frequencies (wavenumbers) in natural order.
    void
    inverse(double[] data)
    Compute the (nomalized) inverse FFT of data, leaving it in place.
    void
    toNaturalOrder(double[] data)
    Reorder and normalize the transformed data from most negative frequency to most positive frequency leaving the result in data.
    void
    transform(double[] data)
    Compute the Fast Fourier Transform of 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

    • FFT2D

      public FFT2D(int nrows, int ncols)
      Create an FFT for transforming nrows*ncols points of Complex, double precision data.
      Parameters:
      nrows -
      ncols -

  • Method Details

    • checkData

      protected void checkData(double[] data, int rowspan)

    • transform

      public void transform(double[] data)
      Compute the Fast Fourier Transform of data leaving the result in data. The array data must be dimensioned (at least) 2*nrows*ncols, consisting of alternating real and imaginary parts.
      Parameters:
      data -

    • backtransform

      public void backtransform(double[] data)
      Compute the (unnomalized) inverse FFT of data, leaving it in place.
      Parameters:
      data -

    • inverse

      public void inverse(double[] data)
      Compute the (nomalized) inverse FFT of data, leaving it in place.
      Parameters:
      data -

    • getFreqMin

      public double getFreqMin(double min, double max, int n)
      Gets the minimum frequency given the domain and the number of points.
      Parameters:
      min - double
      max - double
      n - int
      Returns:
      double

    • getFreqMax

      public double getFreqMax(double min, double max, int n)
      Gets the maximum frequency given the domain and the number of points.
      Parameters:
      min - double
      max - double
      n - int
      Returns:
      double

    • getNaturalModes

      public double[] getNaturalModes(int n)
      Gets an array containing the mode numbers in natural order.
      Returns:
      array of mode numbers

    • getWrappedModes

      public double[] getWrappedModes(int n)
      Gets an array containing the mode numbers in wrap-around order.
      Returns:
      array of mode numbers

    • getWrappedOmegaX

      public double[] getWrappedOmegaX(double xmin, double xmax)
      Gets an array containing the angular frequencies (wavenumbers) 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

    • getWrappedOmegaY

      public double[] getWrappedOmegaY(double ymin, double ymax)
      Gets an array containing the angular frequencies (wavenumbers) in natural order. The first data point is at ymin and the last data point is at ymax.
      Parameters:
      ymin -
      ymax -
      Returns:
      the array of frequencies

    • getWrappedFreq

      public double[] getWrappedFreq(double delta, int n)
      Gets an array containing the frequencies in wrap-around order. Samples in the data are separated by delta.
      Parameters:
      delta -
      Returns:
      the array of frequencies

    • getNaturalFreqX

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

    • getNaturalFreqX

      public double[] getNaturalFreqX(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

    • getNaturalOmegaX

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

    • getNaturalOmegaX

      public double[] getNaturalOmegaX(double xmin, double xmax)
      Gets an array containing the angular frequencies (wavenumbers) 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

    • getNaturalFreqY

      public double[] getNaturalFreqY(double delta)
      Gets an array containing the frequencies in natural order if samples in the orginal data are separated by delta in y.
      Parameters:
      delta -
      Returns:
      the array of frequencies

    • getNaturalFreqY

      public double[] getNaturalFreqY(double ymin, double ymax)
      Gets an array containing the frequencies in natural order. The first data point is at ymin and the last data point is at ymax.
      Parameters:
      ymin -
      ymax -
      Returns:
      the array of frequencies

    • getNaturalOmegaY

      public double[] getNaturalOmegaY(double delta)
      Gets an array containing the frequencies in natural order if samples in the orginal data are separated by delta in y.
      Parameters:
      delta -
      Returns:
      the array of frequencies

    • getNaturalOmegaY

      public double[] getNaturalOmegaY(double ymin, double ymax)
      Gets an array containing the frequencies in natural order. The first data point is at ymin and the last data point is at ymax.
      Parameters:
      ymin -
      ymax -
      Returns:
      the array of frequencies

    • toNaturalOrder

      public void toNaturalOrder(double[] data)
      Reorder and normalize the transformed data from most negative frequency to most positive frequency leaving the result in data.
      Parameters:
      data -