[bug #68196] Wrong phase in bode plot

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Follow-up Comment #2, bug #68196 (group octave):

I might be wrong but to me it looks like a bug in `bode.m`.
Continuous time integrator is `1/z` but for discrete 
it is `1/(z-1)`. So bode should count poles at `1` for discrete system. So
change:

n_poles_at_origin = sum (all_poles{h} == 0);
    n_zeros_at_origin = sum (all_zeros{h} == 0);
    asymptotic_low_freq_phase = (n_zeros_at_origin - n_poles_at_origin)*90;

to

    if (isct (sys1))
      ## Continuous systems have integrators at s = 0
      n_poles_at_origin = sum (abs (all_poles{h}) < eps);
      n_zeros_at_origin = sum (abs (all_zeros{h}) < eps);
    else
      ## Discrete systems have integrators at z = 1
      n_poles_at_origin = sum (abs (all_poles{h} - 1) < eps);
      n_zeros_at_origin = sum (abs (all_zeros{h} - 1) < eps);
    endif
    asymptotic_low_freq_phase = (n_zeros_at_origin - n_poles_at_origin)*90;

?

Dmitri.
-- 



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