% Matlab programs for Chapter 1
% Date: 2/25/04
% File: Chap01.m
% Name: Feng-Li Lian (fengli@ntu.edu.tw)

echo on

clear all; close all;


%%% scalar

3*5

a = 3

b = 5

a*b

c = a*b

d = a^b
pause

whos
pause


%%% matrix

A = [ 1 2
      3 4 ]
pause

B = [ 5 6 7; 8 9 10 ]
pause

C = [ 5 6 7
      8 9 10 ];
pause

D = [ 2 2
      3 3 ];
pause
  
A * B
C = A * B;

A*D
A.*D
pause

%%% DT exponential signals

 C = 5;
 a = 0.8;
 n = -10:10;
 m = -10:2:10;
pause

 x1 = C*a.^n;
pause

 a = -0.8;

 x2 = C*a.^n;
pause
 
 
%%% figure

plot(x1)
pause

plot(x1,'.')

plot(x1,'o')
pause

stem(x1)
pause

plot(n,x1,'o')

stem(n,x1)
pause

title('Title is HERE')
xlabel('X lable is HERE');
ylabel('Y lable is HERE');
text( 2, 30, 'Here is (2,30)');
pause

stem(n,x1, 'or' ); hold on;
stem(n,x2, 'xb' )
axis([ -15 15 -60 60 ])
hold off;
pause

subplot(2,1,1); %subplot(211)
stem(n,x1,'or')
subplot(2,1,2); 
stem(n,x2,'xb')
pause

subplot(2,2,1); %subplot(211)
stem(n,x1,'or')
subplot(2,2,4); 
stem(n,x2,'xb')
pause


%%% DT sinusodal signals

 n = -15:15;

 x1 = cos(0*n);
 x2 = cos(pi*n/8);
 x3 = cos(pi*n/4);
 x4 = cos(pi*n/2);
 x5 = cos(pi*n);
 x6 = cos(3*pi*n/2);
 x7 = cos(7*pi*n/4);
 x8 = cos(15*pi*n/8);
 x9 = cos(2*pi*n);
 
%%% figure

close 

subplot(3,3,1);  stem(n,x1,'or'); axis([-15 15 -1 1]);
subplot(3,3,2);  stem(n,x2,'or'); axis([-15 15 -1 1]);
subplot(3,3,3);  stem(n,x3,'or'); axis([-15 15 -1 1]);

n = -15:15;
x = zeros(9,length(n));
w = [ 0  pi/8  pi/4  pi/2  pi  3*pi/2  7*pi/4  15*pi/8  2*pi ];

close

for i = 1:9
    x(i,1:end) = cos(w(i)*n);
    subplot(3,3,i); stem(n,x(i,:), 'ob' ); axis( [ -15 15 -1.5 1.5 ] );
    title( ['x[n] = cos(' num2str(w(i)) 'n)'] ); 
    if i==1
        pause
    else
        pause(1)
    end
end