Signal Plots: swanalplot.m

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Signal Plots: swanalplot.m

Figure J.13 lists a Matlab script for plotting input and output signals for the simplest lowpass filter in §2.2, used in Fig.2.4 to produce Fig.2.5. This is not really a ``utility'' since it relies on global variables. It is instead a script containing mundane plotting code that was omitted from Fig.2.4 to make it fit on one page. I include it only because people keep asking for it! The script is compatible with Matlab only.

**Figure:** Matlab script for plotting input/output signals in Fig.2.5.
%swanalplot.m - plots needed by swanal.m doplots = 1; % set to 0 to skip plots dopause = 0; % set to 1 to pause after each plot if doplots figure(gcf); subplot(2,1,1); ttl=sprintf('Filter Input Sinusoid, f(%d)=%0.2f',k,f(k)); myplot(t,s,'k',ttl); tinterp=0:(t(2)-t(1))/10:t(end); % interpolated time axis si = ampincos(2pif(k)tinterp+phasein); % for plot text(-1.5,0,'(a)'); hold on; plot(tinterp,si,'--k'); hold off; subplot(2,1,2); ttl='Filter Output Sinusoid'; myplot(t,y,'k',ttl); text(-1.5,0,'(b)'); if dopause, disp('PAUSING - [RETURN] to continue . . .'); pause; end saveplot(sprintf('../eps/swanal-%d.eps',k)); end

Figure: Matlab script for plotting input/output signals in Fig.2.5.

%swanalplot.m - plots needed by swanal.m

doplots = 1; % set to 0 to skip plots
dopause = 0; % set to 1 to pause after each plot
if doplots
  figure(gcf);
  subplot(2,1,1);
  ttl=sprintf('Filter Input Sinusoid, f(%d)=%0.2f',k,f(k));
  myplot(t,s,'*k',ttl);
  tinterp=0:(t(2)-t(1))/10:t(end); % interpolated time axis
  si = ampin*cos(2*pi*f(k)*tinterp+phasein); % for plot
  text(-1.5,0,'(a)');
  hold on; plot(tinterp,si,'--k'); hold off;
  subplot(2,1,2);
  ttl='Filter Output Sinusoid';
  myplot(t,y,'*k',ttl);
  text(-1.5,0,'(b)');
  if dopause, disp('PAUSING - [RETURN] to continue . . .'); 
  pause; end
  saveplot(sprintf('../eps/swanal-%d.eps',k));
end

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written by Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.

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Introduction to Digital Filters
Matlab Utilities
Signal Plots: swanalplot.m