plotbode.m

控制系统计算机辅助设计——MATLAB语言与应用(源代码）

function plotbode(w,mag,ph,linetype)
%PLOTBODE       Plot Bode diagrams.
%       PLOTBODE(W,MAG,PH,'linetype') plots 20*log10(MAG) and PH in
%       Bode format, with grids and labels. W is the frequency vector.
%       MAG and PH can be either vectors or matrices.
%       `linetype' is optional. If it is present it is used to set 
%       the plot line or point type. See PLOT for valid line types.
%
%       The two plots are drawn one above the other.
%
%       PLOTBODE(W,C,'linetype') plots Bode plots of the
%       complex matrix or vector C. In this form UNWRAP is applied
%       to the phase before plotting.
%
%       See also PLOTDB,PLOTNYQ,PLOTNIC,UNWRAP

%       Dr M.P. Ford 4th August 1987, Revised J.M.Maciejowski,13 Jan 1988.
% Copyright (c) 1987,1993 by GEC Engineering Research Centre and 
% Cambridge Control Ltd. All Rights Reserved.
% History: 
%   Two plots now drawn simultaneously in one figure, 12.7.93, JMM.
%   `Help' documentation corrected slightly: units of PH are not
%       knnown to plotbode. 10.7.93, JMM.
%   `fixphase' replaced by `unwrap'. 29.5.93,JMM.
%   MRN0015

nargs=nargin;
error(nargchk(2,4,nargs));

[m,n]=size(mag);
if (length(w)~=m)&(length(w)~=n)
   error('Frequency vector does not match points, did you forget FGET?')
end

if nargs==2
  linetype=' ';
  [mag,ph]=r2p(mag);  % ph is in degrees
  ph=(180/pi)*unwrap(ph*pi/180);%`fixphase' replaced by `unwrap'.29.5.93,JMM.
end % if nargs==2

if nargs==3
  if isstr(ph)
    linetype=ph;
    [mag,ph]=r2p(mag); % ph is in degrees
    ph=(180/pi)*unwrap(ph*pi/180);%`fixphase'replaced by `unwrap'.29.5.93,JMM.
  else
    linetype=' ';
  end
end  % if nargs ==3


if linetype==' '  % do not have linetype
   subplot(2,1,1)
   semilogx(w,20*log10(mag)),grid,xlabel('FREQUENCY'),ylabel('MAG dB')
   subplot(2,1,2)
   semilogx(w,ph),grid,xlabel('FREQUENCY'),ylabel('PHASE')
else
   subplot(2,1,1)
   semilogx(w,20*log10(mag),linetype),grid,xlabel('FREQUENCY'),...
   ylabel('MAG dB')
   subplot(2,1,2)
   semilogx(w,ph,linetype),grid,xlabel('FREQUENCY'),ylabel('PHASE')
end