edu.udo.cs.yale.tools.math
Class FastFourierTransform

java.lang.Object
  edu.udo.cs.yale.tools.math.FastFourierTransform

public class FastFourierTransform
extends java.lang.Object

Performs a FastFourierTransform on an array of complex values. The runtime is O(n log n).

The used direction simply defines used norm factors, it can be omitted but the resulting values may be quantitative wrong.

Version:

$Id: FastFourierTransform.java,v 1.8 2006/03/27 13:22:03 ingomierswa Exp $

Author:

Ingo Mierswa

Field Summary

static int	FREQUENCY2TIME Specifies the transformation from frequency into time domain.
static int	TIME2FREQUENCY Specifies the transformation from time into frequency domain.
private int	windowFunctionType The window function which should be applied before calculating the FT.

Constructor Summary

FastFourierTransform(int windowFunctionType)

Method Summary

private int	bitrev(int j, double nu) Calculates ...
static double	convertFrequency(double frequency, int nyquist, int totalLength) Normalizes the frequency to the correct value.
Complex[]	getFourierTransform(Complex[] series, int direction, int functionType) Performs a fourier transformation in the specified direction.
Complex[]	getFourierTransform(ExampleSet exampleSet, Attribute source, Attribute target) Builds the fourier transform from the values of the first attribute onto the second.
static int	getGreatestPowerOf2LessThan(int n) Calculates the greatest power of 2 which is smaller than the given number.

Methods inherited from class java.lang.Object

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

Field Detail

TIME2FREQUENCY

public static final int TIME2FREQUENCY

Specifies the transformation from time into frequency domain.

See Also:

Constant Field Values

FREQUENCY2TIME

public static final int FREQUENCY2TIME

Specifies the transformation from frequency into time domain.

See Also:

Constant Field Values

windowFunctionType

private int windowFunctionType

The window function which should be applied before calculating the FT.

Constructor Detail

FastFourierTransform

public FastFourierTransform(int windowFunctionType)

Method Detail

getFourierTransform

public Complex[] getFourierTransform(ExampleSet exampleSet,
                                     Attribute source,
                                     Attribute target)
                              throws OperatorException

Builds the fourier transform from the values of the first attribute onto the second.

Throws:

OperatorException

convertFrequency

public static double convertFrequency(double frequency,
                                      int nyquist,
                                      int totalLength)

Normalizes the frequency to the correct value.

getFourierTransform

public Complex[] getFourierTransform(Complex[] series,
                                     int direction,
                                     int functionType)
                              throws OperatorException

Performs a fourier transformation in the specified direction. The window function type defines one of the possible window functions.

Throws:

OperatorException

getGreatestPowerOf2LessThan

public static int getGreatestPowerOf2LessThan(int n)

Calculates the greatest power of 2 which is smaller than the given number.

bitrev

private int bitrev(int j,
                   double nu)

Calculates ...