gusucode.com > 信号处理工具箱 - signal源码程序 > signal\signal\signal\zplane.m
function [h1, h2, h3]=zplane(z,p,ax);
%ZPLANE Z-plane zero-pole plot.
% ZPLANE(Z,P) plots the zeros Z and poles P (in column vectors) with the
% unit circle for reference. Each zero is represented with a 'o' and
% each pole with a 'x' on the plot. Multiple zeros and poles are
% indicated by the multiplicity number shown to the upper right of the
% zero or pole. ZPLANE(Z,P) where Z and/or P is a matrix plots the zeros
% or poles in different columns with different colors.
%
% ZPLANE(B,A) where B and A are row vectors containing transfer function
% polynomial coefficients plots the poles and zeros of B(z)/A(z). Note
% that if B and A are both scalars they will be interpreted as Z and P.
%
% [H1,H2,H3]=ZPLANE(Z,P) returns vectors of handles to the lines and
% text objects generated. H1 is a vector of handles to the zeros lines,
% H2 is a vector of handles to the poles lines, and H3 is a vector of
% handles to the axes / unit circle line and to text objects which are
% present when there are multiple zeros or poles. In case there are no
% zeros or no poles, H1 or H2 is set to the empty matrix [].
%
% ZPLANE(Z,P,AX) puts the plot into axes AX.
%
% See also FREQZ.
% Author(s): T. Krauss, 3-19-93
% Copyright (c) 1988-98 by The MathWorks, Inc.
% $Revision: 1.5 $ $Date: 1998/12/23 22:37:03 $
error(nargchk(1,3,nargin))
tf = 0; % By default assume inputs are poles and zeros
prodsz = prod(size(z));
colsz = size(z,2);
switch nargin,
case 1,
% Only Z was specified, check if it is indeed Z or if it is a numerator
if (prodsz==colsz)&(~(prodsz == 1)),
% Row vector, num specified
p = 1;
tf = 1; % Set TF flag
else
% Scalar or column vector, interpret as Z
p = [];
end
case 2,
prodsp = prod(size(p));
colsp = size(p,2);
if xor(prodsz == 1,prodsp == 1),
% One of the inputs is a scalar but not both,
if (prodsz==colsz)&(prodsp==colsp),
% The other input is a row, TF specified
tf = 1; % Set TF flag
end
elseif ~((prodsz == 1)&(prodsp == 1)),
% No scalars specified
if (prodsz==colsz)&(prodsp==colsp),
% num and den specified
tf = 1; % Set TF flag
elseif (prodsz==colsz)|(prodsp==colsp),
% A row vector was specified with a column vector, this is not allowed
error('When specifying polynomials, both vectors must be rows.');
end
end
end
if tf == 1,
% TF was specified, convert to z,p,k
% Catch cases when the num or den are zero.
if max(abs(p)) == 0,
% Divide by zero not allowed
error('Denominator cannot be zero.');
elseif max(abs(z)) == 0,
% num is zero, there are no poles
p = 1;
end
% Pad A or B with trailing zeros if B and A are of different length
if length(z) < length(p)
z = [z zeros(1,length(p)-length(z))];
elseif length(p) < length(z)
p = [p zeros(1,length(z)-length(p))];
end
% Remove trailing zeros if both num and den have them
while z(end) == 0 & p(end) == 0,
z(end) = [];
p(end) = [];
end
% Find Poles and Zeros
z = roots(z);
p = roots(p);
end
if ~any(imag(z)),
z = z + j*1e-50;
end;
if ~any(imag(p)),
p = p + j*1e-50;
end;
if nargin < 3
ax = newplot;
else
axes(ax)
end
kids = get(ax,'Children');
for i = 1:length(kids)
delete(kids(i));
end
set(ax,'box','on')
set(ax,'xlimmode','auto','ylimmode','auto')
% equivalent of 'hold on':
set(ax,'nextplot','add')
set(get(ax,'parent'),'nextplot','add')
if ~isempty(z),
zh = plot(z,'o','markersize',7);
else
zh = [];
end
if ~isempty(p),
ph = plot(p,'x','markersize',8);
else
ph = [];
end
theta = linspace(0,2*pi,70);
oh = plot(cos(theta),sin(theta),':');
% inline 'axis equal'
units = get(ax,'Units'); set(ax,'Units','Pixels')
apos = get(ax,'Position'); set(ax,'Units',units)
set(ax,'DataAspectRatio',[1 1 1],...
'PlotBoxAspectRatio',apos([3 4 4]))
% zoom out ever so slightly (5%)
if apos(3) < apos(4)
yl=get(ax,'ylim');
d=diff(yl);
yl = [yl(1)-.05*d yl(2)+.05*d];
set(ax,'ylim',yl);
xl = get(ax,'xlim');
else
xl=get(ax,'xlim');
d=diff(xl);
xl = [xl(1)-.05*d xl(2)+.05*d];
set(ax,'xlim',xl);
yl = get(ax,'ylim');
end
set(oh,'xdat',[get(oh,'xdat') NaN ...
xl(1)-diff(xl)*100 xl(2)+diff(xl)*100 NaN 0 0]);
set(oh,'ydat',[get(oh,'ydat') NaN 0 0 NaN ...
yl(1)-diff(yl)*100 yl(2)+diff(yl)*100]);
handle_counter = 2;
fuzz = diff(xl)/80; % horiz spacing between 'o' or 'x' and number
fuzz=0;
[r,c]=size(z);
if (r>1)&(c>1), % multiple columns in z
ZEE=z;
else
ZEE=z(:); c = min(r,c);
end;
for which_col = 1:c, % for each column of ZEE ...
z = ZEE(:,which_col);
[mz,z_ind]=mpoles(z);
for i=2:max(mz),
j=find(mz==i);
for k=1:length(j),
x = real(z(z_ind(j(k)))) + fuzz;
y = imag(z(z_ind(j(k))));
if (j(k)~=length(z)),
if (mz(j(k)+1)<mz(j(k))),
oh(handle_counter) = text(x,y,num2str(i));
handle_counter = handle_counter + 1;
end
else
oh(handle_counter) = text(x,y,num2str(i));
handle_counter = handle_counter + 1;
end
end
end
end
[r,c]=size(p);
if (r>1)&(c>1), % multiple columns in z
PEE=p;
else
PEE=p(:); c = min(r,c);
end;
for which_col = 1:c, % for each column of PEE ...
p = PEE(:,which_col);
[mp,p_ind]=mpoles(p);
for i=2:max(mp),
j=find(mp==i);
for k=1:length(j),
x = real(p(p_ind(j(k)))) + fuzz;
y = imag(p(p_ind(j(k))));
if (j(k)~=length(p)),
if (mp(j(k)+1)<mp(j(k))),
oh(handle_counter) = text(x,y,num2str(i));
handle_counter = handle_counter + 1;
end
else
oh(handle_counter) = text(x,y,num2str(i));
handle_counter = handle_counter + 1;
end
end
end
end
set(oh(2:length(oh)),'vertical','bottom');
if (nargout==1),
h1 = zh;
elseif (nargout==2),
h1 = zh;
h2 = ph;
elseif (nargout==3),
h1 = zh;
h2 = ph;
h3 = oh;
end
set(get(ax,'xlabel'),'string','Real Part')
set(get(ax,'ylabel'),'string','Imaginary Part')
set(ax,'nextplot','replace')
set(get(ax,'parent'),'nextplot','replace')