Section: Handle-Based Graphics
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