## ZPLANE Zero-pole plot

Section: Handle-Based Graphics

### Usage

This function makes a zero-pole plot of a discrete-time system defined by its zeros and poles. The various syntaxes are

        zplane(z,p)

where `z` and `p` are the zeros and the poles of the system stored as column vectors, or

        zplane(b,a)

where `a` and `b` are the polynomial coefficients of the numerator and denominator stored as line vectors (`roots` is used to find the zeros and poles). The symbol `'o'` represents a zero and the symbol `'x'` represents a pole. The plot includes the unit circle for reference. Contributed by Paulo Xavier Candeias under GPL