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## [Help-gsl] Quick FFT question

**From**: |
Nghia Ho |

**Subject**: |
[Help-gsl] Quick FFT question |

**Date**: |
Tue, 22 Jul 2008 09:37:42 -0700 (PDT) |

Hi,
I need to implement an algorithm that makes use of the FFT to do some basic
signal processing. Basically, given an array of numbers I would like to extract
the coefficients of the N lowest frequency components.
The GSL document says the results are laid out such that index from 0 to N/2
are the positive frequencies and the rest are negative. My mathematical
knowledge of FFT is limited so please bare with me on the next question. I see
the real values are the same for both positive/negative side, but imaginary
values flip. So if I take the magnitude (|Re + Imz|) of the first N values of
the positive side would that give me what I want?
Thanks,
Nghia

**[Help-gsl] Quick FFT question**,
*Nghia Ho* **<=**