The zplane function plots poles and zeros of a linear system. For example, a simple filter with a zero at -1/2 and a complex pole pair at 0.9e–j2π(0.3) and 0.9ej2π(0.3) is
zer = -0.5; pol = 0.9*exp(j*2*pi*[-0.3 0.3]');
To view the pole-zero plot for this filter you can use
or, for access to additional tools, use fvtool. First convert the poles and zeros to transfer function form, then call fvtool,
[b,a] = zp2tf(zer,pol,1); fvtool(b,a)
and click the Pole/Zero Plot toolbar button on the toolbar or select Analysis > Pole/Zero Plot to see the plot.
For a system in zero-pole form, supply column vector arguments z and p to zplane:
For a system in transfer function form, supply row vectors b and a as arguments to zplane:
In this case zplane finds the roots of b and a using the roots function and plots the resulting zeros and poles.
See Linear System Models for details on zero-pole and transfer function representation of systems.