First, 'bode' is going to give you a Bode plot, and it's going to be insistent on giving it to you in log-log format -- so if you want a plot on a linear frequency axis from -pi to +pi, then you need to do it by hand. Second, 'bode' is pretty insistent about reporting things as per second -- if you define a system as 'd' then it'll act like the system is sampled at 1Hz. If, for instance, you run: H = syslin('d', (%z - 0.9) / (%z - 1)); g = scf(0); clf; bode(H, 0.001, 0.4999, 'rad') You will get the following plot: It puts the vertical red lines there, presumably to mark Nyquist, even though we're displaying in radians per sample, and it reports things as radians/s. You can get into the guts of the graph and fix it up, though: delete(g.children(2).children(1)); // Delete the top red line delete(g.children(1).children(1)); // Delete the bottom red line g.children(2).x_label.text = "Frequency (rad/sample)"; // Change the top text g.children(1).x_label.text = "Frequency (rad/sample)"; // change the bottom text Do all this, and you get: On Sat, 2017-02-25 at 20:38 +0100, Serge Steer wrote: > Le 25/02/2017 à 19:17, Pablo Fonovich a écrit : > > Hi: > > This is the first time i work with discrete time transfers > > functions and Scilab. > > I want to use bode() for plotting the magnitud and phase response > > of the system, however, i don't understand how to set the > > frequencies to normalized values (-pi, pi). > > This is what i'm doing: > > > > s=poly(0,'s') > > H=(s^(-2400))/(1-0.5*s^(-2400)) > > S=syslin('d',H) > > bode(S) > > > > i get a warning that frequencies beyond nyquist rate are ignored > > and the resulting plot is attached. > > > > In the help, it says that bode parameter could include fmin and > > fmax in herz, but isn't a discrete system response limited to > > normalized frequencies? And to transform the normalized frecuency > > to herz the sample rate must be used, but i don't know how to pass > > it to the system or something. > S=syslin(dt,H) defines a dynamical system sampled. dt beeing the > sampling period in second. > If you want the frequency uniis be in rd/s add "rad" as last input > argument > > Any hints would be appreciated. > > Thanks > > > > > > _______________________________________________ > > 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 --
Tim Wescott www.wescottdesign.com Control & Communications systems, circuit & software design. Phone: 503.631.7815 Cell: 503.349.8432
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