Feature request: Add pole-zero plot

[mxxmxn]

I don't know if it fits in this package, but it would be great to add pole-zero plots.

A basic example looks as follows:

Ideally, the scaling would be logarithmic or linear with the Option for different tik labels (dB or powers of ten) and the matching tiks/grid. Please make the positive/negative sections of a axis configurable to cover separate values (like $-10^5$ to $-10^1$ on negative real axis and $10^{-3}$ to $10^1$ on positive real axis).

[rlkamalapurkar]

It does, I just haven't had time to add something like this. If transfer functions are passed using the zpk format, it should be doable.

If they are passed in tf format, I am not so sure. LaTeX wasn't made for things like finding roots of polynomials :-)

I can try to hack together a solution for the zpk format, but it might be a while!

[mxxmxn]

Sounds great.
I think zpk format is sufficient. There are other solutions to convert a tf in zpk, so I think there is no need to do it in LaTeX.