代码：
x1 = [1,2,2]; x2 = [1,2,3,4]; y1 = circonvt(x1,x2,5); % N = 5 n1 = 0:1:length(x1)-1;
n2 = 0:1:length(x2)-1; ny1 = 0:1:length(y1)-1; %% -----------------------------------------------------------------
%% START a
%% -----------------------------------------------------------------
figure('NumberTitle', 'off', 'Name', 'Exameple5.15a ')
set(gcf,'Color','white');
subplot(3,1,1); stem(n1,x1); title('sequence x1(n)'); axis([0,5,0,5]);
xlabel('n'); ylabel('x1(n)'); grid on;
subplot(3,1,2); stem(n2,x2); title('sequence x2(n)'); axis([0,5,0,5]);
xlabel('n'); ylabel('x2(n)'); grid on;
subplot(3,1,3); stem(ny1,y1); title('Circularly convolution sequence y1(n)'); axis([0,5,0,20]);
xlabel('n'); ylabel('y1(n)'); grid on; %% -----------------------------------------------------------------
%% END a
%% ----------------------------------------------------------------- y2 = circonvt(x1,x2,6); % N = 6 ny2 = 0:1:length(y2)-1; %% -----------------------------------------------------------------
%% START b
%% -----------------------------------------------------------------
figure('NumberTitle', 'off', 'Name', 'Exameple5.15b ')
set(gcf,'Color','white');
subplot(3,1,1); stem(n1,x1); title('sequence x1(n)'); axis([0,5,0,5]);
xlabel('n'); ylabel('x1(n)'); grid on;
subplot(3,1,2); stem(n2,x2); title('sequence x2(n)'); axis([0,5,0,5]);
xlabel('n'); ylabel('x2(n)'); grid on;
subplot(3,1,3); stem(ny2,y2); title('Circularly convolution sequence y2(n)'); axis([0,5,0,20]);
xlabel('n'); ylabel('y2(n)'); grid on; %% -----------------------------------------------------------------
%% END b
%% -----------------------------------------------------------------
结果：
