From: Alex Polite <notmyprivateemail@...>
Date: 2006-06-03T03:04:29+09:00
Subject: Re: Time domain to frequency domain with FFT from GSL

On 6/2/06, Adam Shelly <adam.shelly@gmail.com> wrote:
> The items after N/2 are the "negative frequencies"  Some mathematician can
> tell you what that means, but in practical terms, they are a mirror image of
> the first half (at least for audio signals).
> If all you are trying to do is display (or extract information about) the
> spectrum, you can throw the 2nd half of the vector away.
>

OK, so say I'm using the ruby wrapper round FFTW3.

na is my time domain data. Then I can get my freq domain data by this:

FFTW3.fft(na, -1).real[0..na.length/2-1]

Right?

alex

-- 
Alex Polite
http://flosspick.org - finding the right open source