jnt.FFT

Class ComplexDouble2DFFT

java.lang.Object

jnt.FFT.ComplexDouble2DFFT

public class ComplexDouble2DFFT
extends Object

Computes the FFT of 2 dimensional complex, double precision data. 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 and Description
ComplexDouble2DFFT(int nrows, int ncols) Create an FFT for transforming nrows*ncols points of Complex, double precision data.

Method Summary

Methods

Modifier and Type	Method and Description
void	backtransform(double[] data) Compute the (unnomalized) inverse FFT of data, leaving it in place.
void	backtransform(double[] data, int rowspan) Compute the (unnomalized) inverse FFT of data, leaving it in place.
protected void	checkData(double[] data, int rowspan)
void	inverse(double[] data) Compute the (nomalized) inverse FFT of data, leaving it in place.
void	inverse(double[] data, int rowspan) Compute the (nomalized) inverse FFT of data, leaving it in place.
double	normalization() Return the normalization factor.
double[]	toWraparoundOrder(double[] data) Return data in wraparound order.
double[]	toWraparoundOrder(double[] data, int rowspan) Return data in wraparound order.
void	transform(double[] data) Compute the Fast Fourier Transform of data leaving the result in data.
void	transform(double[] data, int rowspan) 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 Detail

ComplexDouble2DFFT

public ComplexDouble2DFFT(int nrows,
                  int ncols)

Create an FFT for transforming nrows*ncols points of Complex, double precision data.

Method Detail

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.

transform

public void transform(double[] data,
             int rowspan)

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.

toWraparoundOrder

public double[] toWraparoundOrder(double[] data)

Return data in wraparound order.

See Also:

wraparound format

toWraparoundOrder

public double[] toWraparoundOrder(double[] data,
                         int rowspan)

Return data in wraparound order. rowspan is used to traverse data; the new array is in packed (rowspan = 2*ncols) format.

See Also:

wraparound format

backtransform

public void backtransform(double[] data)

Compute the (unnomalized) inverse FFT of data, leaving it in place.

backtransform

public void backtransform(double[] data,
                 int rowspan)

Compute the (unnomalized) inverse FFT of data, leaving it in place.

normalization

public double normalization()

Return the normalization factor. Multiply the elements of the backtransform'ed data to get the normalized inverse.

inverse

public void inverse(double[] data)

Compute the (nomalized) inverse FFT of data, leaving it in place.

inverse

public void inverse(double[] data,
           int rowspan)

Compute the (nomalized) inverse FFT of data, leaving it in place.