visad.math

Class FFT

java.lang.Object

visad.math.FFT

public class FFT
extends java.lang.Object

FFT is the VisAD class for Fourier Transforms, using the Fast Fourier Transform when the domain length is a power of two.

Constructor Summary

Constructors

Constructor and Description
FFT()

Method Summary

Modifier and Type	Method and Description
static FlatField	backwardFT(Data[] datums) for use by SpreadSheet only - ordinary applications should use other method signatures; invoke in SpreadSheet by: link(visad.math.FFT.backwardFT(A1))
static double[][]	FFT1D(double[][] x, boolean forward) compute 1-D FFT transform length (2nd dimension of x) must be a power of 2
static float[][]	FFT1D(float[][] x, boolean forward) compute 1-D FFT transform length (2nd dimension of x) must be a power of 2
static FlatField	forwardFT(Data[] datums) for use by SpreadSheet only - ordinary applications should use other method signatures; invoke in SpreadSheet by: link(visad.math.FFT.forwardFT(A1))
static FlatField	fourierTransform(Field field, boolean forward) return Fourier Transform of field, use FFT if domain dimension(s) are powers of 2
static FlatField	fourierTransform(Field field, boolean forward, FunctionType ftype, GriddedSet domain_set, CoordinateSystem range_coord_sys, Set[] range_sets, Unit[] units) return Fourier Transform of field, use FFT if domain dimension(s) are powers of 2
static double[][]	FT1D(double[][] x, boolean forward) compute 1-D Fourier transform use FFT if length (2nd dimension of x) is a power of 2
static float[][]	FT1D(float[][] x, boolean forward) compute 1-D Fourier transform use FFT if length (2nd dimension of x) is a power of 2
static double[][]	FT2D(int rows, int cols, double[][] x, boolean forward) compute 2-D Fourier transform, calling 1-D FT twice use FFT if rows and cols are powers of 2
static float[][]	FT2D(int rows, int cols, float[][] x, boolean forward) compute 2-D Fourier transform, calling 1-D FT twice use FFT if rows and cols are powers of 2
static void	main(java.lang.String[] args) test Fourier Transform methods

Methods inherited from class java.lang.Object

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

Constructor Detail

FFT

public FFT()

Method Detail

forwardFT

public static FlatField forwardFT(Data[] datums)

for use by SpreadSheet only - ordinary applications should use other method signatures; invoke in SpreadSheet by: link(visad.math.FFT.forwardFT(A1))

backwardFT

public static FlatField backwardFT(Data[] datums)

for use by SpreadSheet only - ordinary applications should use other method signatures; invoke in SpreadSheet by: link(visad.math.FFT.backwardFT(A1))

fourierTransform

public static FlatField fourierTransform(Field field,
                                         boolean forward)
                                  throws VisADException,
                                         java.rmi.RemoteException

return Fourier Transform of field, use FFT if domain dimension(s) are powers of 2

Parameters:

field - Field with domain dimension = 1 (1-D FT) or 2 (2-D FT) and 1 (real part) or 2 (real & imaginary) range RealTypes

forward - true for forward and false for backward

Returns:

Fourier transform of field

Throws:

VisADException - a VisAD error occurred

java.rmi.RemoteException - an RMI error occurred

fourierTransform

public static FlatField fourierTransform(Field field,
                                         boolean forward,
                                         FunctionType ftype,
                                         GriddedSet domain_set,
                                         CoordinateSystem range_coord_sys,
                                         Set[] range_sets,
                                         Unit[] units)
                                  throws VisADException,
                                         java.rmi.RemoteException

return Fourier Transform of field, use FFT if domain dimension(s) are powers of 2

Parameters:

field - Field with domain dimension = 1 (1-D FT) or 2 (2-D FT) and 1 (real part) or 2 (real & imaginary) range RealTypes

forward - true for forward and false for backward

ftype - use for return Field (may be null)

domain_set - use for return Field (may be null)

range_coord_sys - use for return Field (may be null)

range_sets - use for return Field (may be null)

units - use for return Field (may be null)

Returns:

Fourier transform of field

Throws:

VisADException - a VisAD error occurred

java.rmi.RemoteException - an RMI error occurred

FT2D

public static float[][] FT2D(int rows,
                             int cols,
                             float[][] x,
                             boolean forward)
                      throws VisADException

compute 2-D Fourier transform, calling 1-D FT twice use FFT if rows and cols are powers of 2

Parameters:

rows - first dimension for 2-D

cols - second dimension for 2-D

x - array for take Fourier transform of, dimensioned [2][length] where length = rows * cols, and the first index (2) is over real & imaginary parts

forward - true for forward and false for backward

Returns:

Fourier transform of x

Throws:

VisADException - a VisAD error occurred

FT2D

public static double[][] FT2D(int rows,
                              int cols,
                              double[][] x,
                              boolean forward)
                       throws VisADException

compute 2-D Fourier transform, calling 1-D FT twice use FFT if rows and cols are powers of 2

Parameters:

rows - first dimension for 2-D

cols - second dimension for 2-D

x - array for take Fourier transform of, dimensioned [2][length] where length = rows * cols, and the first index (2) is over real & imaginary parts

forward - true for forward and false for backward

Returns:

Fourier transform of x

Throws:

VisADException - a VisAD error occurred

FT1D

public static float[][] FT1D(float[][] x,
                             boolean forward)
                      throws VisADException

compute 1-D Fourier transform use FFT if length (2nd dimension of x) is a power of 2

Parameters:

x - array for take Fourier transform of, dimensioned [2][length], the first index (2) is over real & imaginary parts

forward - true for forward and false for backward

Returns:

Fourier transform of x

Throws:

VisADException - a VisAD error occurred

FFT1D

public static float[][] FFT1D(float[][] x,
                              boolean forward)
                       throws VisADException

compute 1-D FFT transform length (2nd dimension of x) must be a power of 2

Parameters:

x - array for take Fourier transform of, dimensioned [2][length], the first index (2) is over real & imaginary parts

forward - true for forward and false for backward

Returns:

Fourier transform of x

Throws:

VisADException - a VisAD error occurred

FT1D

public static double[][] FT1D(double[][] x,
                              boolean forward)
                       throws VisADException

compute 1-D Fourier transform use FFT if length (2nd dimension of x) is a power of 2

Parameters:

x - array for take Fourier transform of, dimensioned [2][length], the first index (2) is over real & imaginary parts

forward - true for forward and false for backward

Returns:

Fourier transform of x

Throws:

VisADException - a VisAD error occurred

FFT1D

public static double[][] FFT1D(double[][] x,
                               boolean forward)
                        throws VisADException

compute 1-D FFT transform length (2nd dimension of x) must be a power of 2

Parameters:

x - array for take Fourier transform of, dimensioned [2][length], the first index (2) is over real & imaginary parts

forward - true for forward and false for backward

Returns:

Fourier transform of x

Throws:

VisADException - a VisAD error occurred

main

public static void main(java.lang.String[] args)
                 throws VisADException

test Fourier Transform methods

Throws:

VisADException