fg_03_01.m

英文书《Digital Signal Processing with Examples in MATLAB》附带的MATLAB实例

% fg_03_01
% Chapter 3, example 3.1; Fig. 3.1 - discrete correlation.
n=0:127;
% Waveform values with periodic extension.
X=[ones(1,25),-ones(1,25),zeros(1,78)];
Y=[0:24,25:-1:1,zeros(1,78)]/25;
YY=[Y,Y];
% Correlation function.
for m=0:127
   phi(m+1)=(1/128)*X*YY(m+1:m+128)';
end

% Graphics: m=0, 32, and 64.
sp_fig(1,9,6);
pltno=[1,2,3];
N=128;
m=[0,10,20];
loc=[38,.8; 35,.5; 13,.3];
for i=1:3
   subplot(2,2,pltno(i));
   plot(n,X,n,X,'*',...
        n,YY(m(i)+1:m(i)+N),'.',n,YY(m(i)+1:m(i)+N),'+');
   axis([0,127,-1.5,1.5]); grid;
   set(gca,'fontname','times','fontsize',14);
   xlabel('Sample no. (n)');
   ylabel('Signals x and y');
   ht1=text(52,1.2,['m=',int2str(m(i))]);
   ht2=text(10,1.2,'x'); ht3=text(loc(i,1),loc(i,2),'y');
   set([ht1,ht2,ht3],'fontname','times','fontsize',14);
end
% phi(m) vs. m.
subplot(2,2,4);
plot(n,phi,'*');
hl=line(m,phi(m+1));
axis([0,127,-.2,.2]); grid;
set(gca,'fontname','times','fontsize',14);
xlabel('Time shift (m)');
ylabel('Correlation \phi_{xy}(m)');
set(hl,'linestyle','none','marker','o','markersize',10);