de.gsi.math.spectra

Class Convolution

java.lang.Object

de.gsi.math.spectra.Convolution

Direct Known Subclasses:

HilbertTransform

public class Convolution
extends Object

implementation of the discrete convolution algorithm via the fourier transform

Author:

rstein

Field Summary

Fields

Modifier and Type	Field and Description
org.jtransforms.fft.DoubleFFT_1D	f1dFFT

Constructor Summary

Constructors

Constructor and Description
Convolution()

Method Summary

Modifier and Type	Method and Description
static void	complexMultiply(double[] data1, double[] data2)
static double[]	getDerivativeFilter(int length) computes derivative filter (Fourier Domain)
static double[]	getHilbertFilter(int length) computes the Hilbert transform filter (Fourier Domain)
static double[]	getIdentityFilter(int length) computes the identity filter
static double[]	getLowPassFilter(int length, double frequency) computes low-pass filter (Fourier Domain)
static double[]	getMorletFilter(int length, double f0, double width)
static void	main(String[] args)
protected static double	MorletWaveletFunctionFourier(double frequency, double f0, double width)
void	Test()
double[]	transform(double[] data, double[] filter, boolean cyclicBoundary) implements convolution via FFT transform only the real part of the signal is computed
double[]	transformFull(double[] data, double[] filter, boolean cyclicBoundary) implements convolution via FFT transform only the real and imaginary part of the signal is returned

Methods inherited from class java.lang.Object

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

Field Detail

f1dFFT

public org.jtransforms.fft.DoubleFFT_1D f1dFFT

Constructor Detail

Convolution

public Convolution()

Method Detail

Test

public void Test()

transform

public double[] transform(double[] data,
                          double[] filter,
                          boolean cyclicBoundary)

implements convolution via FFT transform only the real part of the signal is computed

Parameters:

data - the data set

filter - the convolution filter

cyclicBoundary - true: cyclic boundary condition; false: ZOH at boundaries

Returns:

the convoluted data

transformFull

public double[] transformFull(double[] data,
                              double[] filter,
                              boolean cyclicBoundary)

implements convolution via FFT transform only the real and imaginary part of the signal is returned

Parameters:

data - the data set

filter - the convolution filter

cyclicBoundary - true: cyclic boundary condition; false: ZOH at boundaries

Returns:

the convoluted data

complexMultiply

public static void complexMultiply(double[] data1,
                                   double[] data2)

getDerivativeFilter

public static double[] getDerivativeFilter(int length)

computes derivative filter (Fourier Domain)

Parameters:

length - the length of the filter

Returns:

array containing derivative filter kernel

getHilbertFilter

public static double[] getHilbertFilter(int length)

computes the Hilbert transform filter (Fourier Domain)

Parameters:

length - the length of the filter

Returns:

vector containing Hilbert filter kernel

getIdentityFilter

public static double[] getIdentityFilter(int length)

computes the identity filter

Parameters:

length - the length of the filter

Returns:

vector containing identy filter

getLowPassFilter

public static double[] getLowPassFilter(int length,
                                        double frequency)

computes low-pass filter (Fourier Domain)

Parameters:

length - the length of the filter

frequency - cut-off frequency

Returns:

array containing low-pass filter kernel

getMorletFilter

public static double[] getMorletFilter(int length,
                                       double f0,
                                       double width)

main

public static void main(String[] args)

MorletWaveletFunctionFourier

protected static double MorletWaveletFunctionFourier(double frequency,
                                                     double f0,
                                                     double width)