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Info_Mac IV CD-ROM (Pacific HiTech Inc.)(August 1994).iso
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ifft
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1994-04-25
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987b
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ifft:
Syntax: ifft ( X )
ifft ( X , N )
Description:
Ifft utilizes the FFTPACK subroutine CFFTB to compute a
discrete Fourier transform of the input. The output is scaled
by 1/N, so that a call to fft() followed by a call to ifft()
will reproduce the original input.
If ifft 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 CFFTB computes the backward complex discrete
Fourier transform (the Fourier synthesis). equivalently, CFFTB
computes a complex periodic sequence from its Fourier
coefficients.
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 ifft is performed. If X is a MxN matrix
then the N columns of X are ifft'ed.
See Also: fft