[R] fft(x, inv=TRUE)
Ben Bolker
ben at zoo.ufl.edu
Thu Jan 9 03:23:03 CET 2003
I would guess that the imaginary parts are very small -- essentially
numeric error. I sometimes use the following function to get rid of these
tiny, spurious imaginary parts.
chop <- function (x, fuzz = 1e-10)
{
if (is.numeric(x)) {
x
}
else if (is.complex(x)) {
ifelse(abs(Im(x)) < fuzz, Re(x), x)
}
}
On Wed, 8 Jan 2003 PLauren at genelogic.com wrote:
> I started out with a real vector b and then obtained its Fourier transform
> thus
> B<-fft(b)
> When I did
> F<-fft(B, inv=TRUE)
> I expected that F would be the inverse FT of B but it still has imaginary
> components.
>
> Should the inverse FT not be purely real? Am I missing something?
>
> Thanks,
> Peter.
>
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