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java.lang.Objectca.uol.aig.fftpack.RealDoubleFFT_Mixed
ca.uol.aig.fftpack.RealDoubleFFT
FFT transform of a real periodic sequence.
Field Summary | |
double |
norm_factor
norm_factor can be used to normalize this FFT transform. |
Constructor Summary | |
RealDoubleFFT(int n)
Construct a wavenumber table with size n. |
Method Summary | |
void |
bt(Complex1D x,
double[] y)
Backward real FFT transform. |
void |
bt(double[] x)
Backward real FFT transform. |
void |
ft(double[] x)
Forward real FFT transform. |
void |
ft(double[] x,
Complex1D y)
Forward real FFT transform. |
Methods inherited from class java.lang.Object |
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
public double norm_factor
Constructor Detail |
public RealDoubleFFT(int n)
n
- the size of a real data sequence. When n is a multiplication of small
numbers (4, 2, 3, 5), this FFT transform is very efficient.Method Detail |
public void ft(double[] x)
x
- an array which contains the sequence to be transformed. After FFT,
x contains the transform coeffients used to construct n complex FFT coeffients.
public void ft(double[] x, Complex1D y)
x
- an array which contains the sequence to be transformed. After FFT,
x contains the transform coeffients used to construct n complex FFT coeffients.
y
- the first complex (n+1)/2 (when n is odd) or (n/2+1) (when
n is even) FFT coeffients.
The remaining complex FFT coeffients can be obtained by the symmetry relation:
the (n-k)-th complex FFT coeffient is the conjugate of n-th complex FFT coeffient.public void bt(double[] x)
x
- an array which contains the sequence to be transformed. After FFT,
x contains the transform coeffients. Also see the comments of ft(double[])
for the relation between x and complex FFT coeffients.public void bt(Complex1D x, double[] y)
x
- an array which contains the sequence to be transformed. When n is odd, it contains the first
(n+1)/2 complex data; when n is even, it contains (n/2+1) complex data.y
- the real FFT coeffients.
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