Package org.opensourcephysics.numerics

Class FFTReal

java.lang.Object

org.opensourcephysics.numerics.FFTReal

public class FFTReal
extends java.lang.Object

FFTReal computes the discrete Fourier coefficients a[0], ...., a[N/2] and b[1], ...., b[N/2 - 1] of the discrete partial Fourier sum a[0] + a[1]*cos(N/2*omega*x) + Sum (k=1,2,...,N/2-1) (a[2*k] * cos(k * omega * x) + a[2*k+1] * sin(k * omega * x)) given real functional values y[0], ...., y[N-1]. Adapted by W. Christian for use in the OSP project.

Constructor Summary

Constructors

Constructor	Description
FFTReal()	Constructs a real FFT transformation for n data points.
FFTReal(int n)	Constructs a real FFT transformation for n data points.

Method Summary

Modifier and Type	Method	Description
double[]	backtransform(double[] data)	Computes the (unnomalized) inverse FFT of data, leaving it in place.
int	getN()	Gets the number of data points.
double[]	getNaturalFreq(double delta)	Gets an array containing the frequencies in natural order.
double[]	getNaturalFreq(double xmin, double xmax)	Gets an array containing the frequencies in natural order.
double[]	getNaturalOmega(double delta)	Gets an array containing the frequencies in natural order.
double[]	getNaturalOmega(double xmin, double xmax)	Gets an array containing the frequencies in natural order.
double[]	inverse(double[] data)	Computes the (nomalized) inverse FFT of data, leaving it in place.
void	setN(int n)	Sets the number of data points.
double[]	transform(double[] data)	Computes the Fast Fourier Transform of the 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

FFTReal

public FFTReal()

Constructs a real FFT transformation for n data points.

FFTReal

public FFTReal(int n)

Constructs a real FFT transformation for n data points.

Parameters:

n - the number of data points

Method Detail

setN

public void setN(int n)

Sets the number of data points.

Parameters:

n - int

getN

public int getN()

Gets the number of data points.

Returns:

int

transform

public double[] transform(double[] data)

Computes the Fast Fourier Transform of the data leaving the result in data. The given array is returned after it has been transformed.

Parameters:

data - double[] the data to be transformed

Returns:

double[] the data after the FFT

backtransform

public double[] backtransform(double[] data)

Computes the (unnomalized) inverse FFT of data, leaving it in place. The given array is returned after it has been transformed.

Parameters:

data - double[] the data to be transformed

Returns:

double[] the data after the FFT

inverse

public double[] inverse(double[] data)

Computes the (nomalized) inverse FFT of data, leaving it in place. The given array is returned after it has been transformed.

Parameters:

data - double[] the data to be transformed

Returns:

double[] the data after the FFT

getNaturalFreq

public double[] getNaturalFreq(double delta)

Gets an array containing the frequencies in natural order. Data are separated by delta.

Parameters:

delta -

Returns:

the array of frequencies

getNaturalFreq

public double[] getNaturalFreq(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

getNaturalOmega

public double[] getNaturalOmega(double delta)

Gets an array containing the frequencies in natural order. Data are separated by delta.

Parameters:

delta -

Returns:

the array of frequencies

getNaturalOmega

public double[] getNaturalOmega(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