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FFT

compute fast Fourier transform

iFFT

compute inverse fast Fourier transform

 

Calling Sequence

Parameters

Description

Examples

References

Calling Sequence

FFT(m, x, y)

evalhf(FFT(m, var(x), var(y)))

iFFT(m, x, y)

evalhf(iFFT(m, var(x), var(y)))

Parameters

m

-

non-negative integer

x, y

-

arrays of floats indexed from 1 to 2^m

Description

• 

Important: The FFT and iFFT functions have been deprecated.  For FFT, use the superseding functions DiscreteTransforms[FourierTransform] and SignalProcessing[FFT] instead.  For iFFT, use the superseding functions DiscreteTransforms[InverseFourierTransform] and SignalProcessing[InverseFFT] instead. These new functions can compute the fast Fourier transform for sequences of arbitrary length (not restricted to a power of 2).

• 

The FFT(m,x,y) and iFFT(m,x,y) commands compute in place the fast Fourier transform and the inverse fast Fourier transform of a complex sequence of length 2m.

• 

The first argument m should be a non-negative integer and the second and third arguments x and y should be arrays of floats indexed from 1 to 2m .  The array x contains the real part of the complex sequence on input and contains the real part of the fast Fourier transform on output.  The array y contains the imaginary part of the complex sequence on input and contains the imaginary part of the fast Fourier transform on output. Both procedures return 2^m, the number of points in the complex sequence.

• 

These procedures may be invoked with evalhf, which uses the hardware floating-point number system.

Examples

Important: The FFT and iFFT functions have been deprecated.  For FFT, use the superseding functions DiscreteTransforms[FourierTransform] and SignalProcessing[FFT] instead.  For iFFT, use the superseding functions DiscreteTransforms[InverseFourierTransform] and SignalProcessing[InverseFFT] instead.

xarray7.,5.,6.,9.:

yarray0,0,0,0:

FFT2,x,y

4

(1)

printx

27.1.1.1.

(2)

printy

04.0.4.

(3)

iFFT2,x,y

4

(4)

printx

7.0000000005.0000000006.0000000009.000000000

(5)

printy

0.0.0.0.

(6)

References

  

Oppenheim, Allan, V., and Schafer, Ronald W. Digital Signal Processing. New Jersey: Prentice-Hall, 1975.  See Fig. 6.5, p. 332.

See Also

DiscreteTransforms

DiscreteTransforms[FourierTransform]

int

inttrans[laplace]

inttrans[mellin]

Matlab[fft]

SignalProcessing[FFT]

 


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