--- /dev/null
+## Copyright (C) 2009 Lukas F. Reichlin
+##
+## This file is part of LTI Syncope.
+##
+## LTI Syncope is free software: you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## LTI Syncope is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with LTI Syncope. If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} pzmap (@var{sys})
+## @deftypefnx {Function File} {[@var{p}, @var{z}] =} pzmap (@var{sys})
+## Plot the poles and zeros of an LTI system in the complex plane.
+## If no output arguments are given, the result is plotted on the screen.
+## Otherwise, the poles and zeros are computed and returned.
+##
+## @strong{Inputs}
+## @table @var
+## @item sys
+## LTI model.
+## @end table
+##
+## @strong{Outputs}
+## @table @var
+## @item p
+## Poles of @var{sys}.
+## @item z
+## Transmission zeros of @var{sys}.
+## @end table
+## @end deftypefn
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: November 2009
+## Version: 0.1
+
+function [pol_r, zer_r] = pzmap (sys)
+
+ ## TODO: multiplot feature: pzmap (sys1, "b", sys2, "r", ...)
+
+ if (nargin != 1)
+ print_usage ();
+ endif
+
+ if (! isa (sys, "lti"))
+ error ("pzmap: argument must be an LTI system");
+ endif
+
+ pol = pole (sys);
+ zer = zero (sys);
+
+ if (! nargout)
+ pol_re = real (pol);
+ pol_im = imag (pol);
+ zer_re = real (zer);
+ zer_im = imag (zer);
+
+ plot (pol_re, pol_im, "xb", zer_re, zer_im, "or")
+ grid ("on")
+ title (["Pole-Zero Map of ", inputname(1)])
+ xlabel ("Real Axis")
+ ylabel ("Imaginary Axis")
+ else
+ pol_r = pol;
+ zer_r = zer;
+ endif
+
+endfunction