I have uploaded an update which is more conformant to the octave contribution guidelines. mainly the space between function name and the '(' and line length.
One more test is also added.

I like what you have done. But it does not follow octave's codding standard.
Did you write this code, or copy it from somewhere?

Thanks for the patch.
Where did you get these changes from?

When bode and nyquist commands are called without giving explicit frequency values, control package evaluates the frequency response at 500 frequency points which are log spaced with in the (min, max) range. The package adds the natural frequency of the poles/zeroes to the above log spaced vector to ensure the peaks and notches are not missed.
For systems with poles or zeroes with very low damping ratio (close to imaginary axis), frequency points at closer intervals are necessary near the frequency of poles/zeros for a smoother plot. Matlab puts closer points near such frequencies where sharp magnitude or phase change occur.
The submitted patch uses the relation between magnitude or phase with respect to frequency for second order systems to calculate the frequency points from 'equally' spaced magnitude and phase vectors by inverting the relation.
The improvement is visible in the nyquist plots for systems with poles and zeros very very close to imaginary axis. The improvement for bode plots are not so dramatic.