[Scilab-users] fourier series and fft

[paul.carrico at free.fr]

sound interesting ... many thanks for the information 


Paul 

----- Mail original -----

De: "Rafael Guerra" <jrafaelbguerra at hotmail.com> 
À: "Users mailing list for Scilab" <users at lists.scilab.org> 
Envoyé: Vendredi 23 Septembre 2016 13:57:31 
Objet: Re: [Scilab-users] fourier series and fft 



Hi Paul, 

Fyi, Tom Co's simple tutorial: http://www.chem.mtu.edu/~tbco/cm416/fft1.pdf 
shows how to obtain the Fourier coefficients via the fft 

Regards, 
Rafael 

-----Original Message----- 
From: users [mailto:users-bounces at lists.scilab.org] On Behalf Of paul.carrico at free.fr 
Sent: Friday, September 23, 2016 8:45 AM 
To: tim at wescottdesign.com; Users mailing list for Scilab <users at lists.scilab.org> 
Subject: Re: [Scilab-users] fourier series and fft 

Thanks Tim for this answer; well I notice I need to "dig" deeper on that topic 

Paul 

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De: "Tim Wescott " < tim at wescottdesign.com > 
À: "Users mailing list for Scilab" < users at lists.scilab.org > 
Envoyé : Jeudi 22 Septembre 2016 23:17:27 
Objet: Re: [Scilab-users] fourier series and fft 

Hey Paul: 

If you mean the Fourier series of a continuous-time periodic signal (or 
a continuous-time function of finite scope), then no, Scilab doesn't do 
that, because the FFT is different from the Fourier Series. If you have 
a signal that's symbolically defined as f(t) over some span of time, 
then Maxima may help you get a symbolic definition of the Fourier 
Series. 

The FFT is essentially the Fourier series of a sampled-time periodic (or 
finite-scope) signal, so if that sampled-time signal is a sufficiently 
accurate approximation of your continuous-time signal, and if your a0, 
a_k and b_k are defined to match the way that Scilab does the FFT , then 
the real part of the FFT are the a coefficients, and the imaginary part 
are the b coefficients. 

If you gather up half a dozen books that include signal processing, 
especially if some are from applications areas a bit removed from 
"normal" signal processing, you'll find that everyone specifies their 
Fourier stuff differently. So what comes out of Scilab's FFT may not 
match _your_ definitions of a0, etc., but they match _someone's_. 

On Thu, 2016-09-22 at 23:09 +0200, paul.carrico at free.fr wrote: 
> dear all 
> 
> I'm novice in Fourier series and other and my question is probably 
> naive (sorry for this) => I'm wondering if scilab can directly 
> calculate the Fourier coefficient a0, a_k and b_k ? 
> 
> 
> I'm currently doing it "by hand" is order to familiarise myself with 
> it (and I'm looking at the same time to documents on FFT use and 
> rules to refind the 2 natural frequencies of the example here bellow), 
> but it seems I'll need to code the coefficient calculations ... Am I 
> right ? 
> 
> Thanks 
> 
> Paul 

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