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fft
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1994-02-21
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870b
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34 lines
fft:
Syntax: fft ( X )
fft ( X , N )
Description:
Fft utilizes the FFTPACK subroutine CFFTF to compute a
discrete forward Fourier transform of the input.
If fft is used with a second argument, N, then the matrix X is
either padded with zeros, or truncated till it is of length N
(if X is a vector), or has row dimension N (if it is a
matrix).
Subroutine CFFTF computes the forward complex discrete Fourier
transform (the Fourier analysis). equivalently , CFFTF
computes the Fourier coefficients of a complex periodic
sequence.
for j=1,...,n
c(j)=the sum from k=1,...,n of
c(k)*exp(-i*(j-1)*(k-1)*2*pi/n)
where i=sqrt(-1)
The argument X must be a matrix. If X is a row, or column
matrix then a vector fft is performed. If X is a MxN matrix
then the N columns of X are fft'ed.
See Also: ifft