I updated the web: Problems and examples of frequency response (Bode diagram, Nyquist diagram, phase margin, gain margin, lead compensator, lag compensator, lag-lead, Nichols chart, static velocity constant error, resonant peak magnitude, resonant peak frequency, bandwidth) by Scilab (bode, syslin, logspace, nyquist, g_margin, p_margin, show_margins,repfreq, dbphi, tf2ss, chart, black, m_circle, horner)
formatting link