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pzmap.m
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1999-04-29
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# Copyright (C) 1996,1998 A. Scottedward Hodel
#
# This file is part of Octave.
#
# Octave 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 2, or (at your option) any
# later version.
#
# Octave 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 Octave; see the file COPYING. If not, write to the Free
# Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
function [zer,pol]=pzmap(sys)
# function [zer,pol]=pzmap(sys)
# Plots the zeros and poles of a system in the complex plane.
#
# inputs: sys: system data structure
# outputs: if omitted, the poles and zeros are plotted on the screen.
# otherwise, pol, zer are returned as the system poles and zeros.
# (see sys2zp for a preferable function call)
save_val = implicit_str_to_num_ok; # save for later
save_emp = empty_list_elements_ok;
implicit_str_to_num_ok = 1;
empty_list_elements_ok = 1;
if(nargin != 1)
usage("pzmap(sys) or [zer,pol] = pzmap(sys)");
elseif (!is_struct(sys));
error("sys must be in system format");
endif
[zer,pol] = sys2zp(sys);
# force to column vectors, split into real, imaginary parts
zerdata = poldata = [];
if(length(zer))
zer = reshape(zer,length(zer),1);
zerdata = [real(zer(:,1)), imag(zer(:,1))];
endif
if(length(pol))
pol = reshape(pol,length(pol),1);
poldata = [real(pol(:,1)), imag(pol(:,1))];
endif
# determine continuous or discrete plane
vars = "sz";
varstr = vars(is_digit(sys) + 1);
# Plot the data
gset nologscale xy;
if(is_siso(sys))
title(sprintf("Pole-zero map from %s to %s", ...
sysgetsg(sys,"in",1,1), sysgetsg(sys,"out",1,1) ));
endif
xlabel(["Re(",varstr,")"]);
ylabel(["Im(",varstr,")"]);
grid;
# compute axis limits
axis(ax2dlim([zerdata;poldata]));
grid
# finally, plot the data
if(length(zer) == 0)
plot(poldata(:,1), poldata(:,2),"@12 ;poles (no zeros);");
elseif(length(pol) == 0)
plot(zerdata(:,1), zerdata(:,2),"@31 ;zeros (no poles);");
else
plot(zerdata(:,1), zerdata(:,2),"@31 ;zeros;", ...
poldata(:,1), poldata(:,2),"@12 ;poles;");
endif
replot
implicit_str_to_num_ok = save_val; # restore value
empty_list_elements_ok = save_emp;
endfunction