Thanks Tim for this answer; well I notice I need to "dig" deeper on that topic
Paul ----- Mail original ----- De: "Tim Wescott" <t...@wescottdesign.com> À: "Users mailing list for Scilab" <users@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.carr...@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 > > > ######################################################################### > mode(0) > > function y=f(x) > y=2.*sin(2 * %pi * x) - 3.*cos(%pi * x); > endfunction > > periode = 2; > number_of_periodes = 1; > n = periode * number_of_periodes; > > x = [0 : %pi/100 : n]'; > y = f(x); > N = size(x,"*"); > > scf() > plot2d(x,y); > > a = fft(y,-1); > _______________________________________________ > users mailing list > users@lists.scilab.org > http://lists.scilab.org/mailman/listinfo/users -- Tim Wescott www.wescottdesign.com Control & Communications systems, circuit & software design. Phone: 503.631.7815 Cell: 503.349.8432 _______________________________________________ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users _______________________________________________ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
