PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

Time Domain Representation of Continuous and Discrete Signals 67

axis([-1 5 -.2 4.3]);

subplot(2,2,3);

f3=-1.*fn; % creates -f(n)

plot(n,f3);title(‘-f(n) vs. n’);

axis([-1 5 -2.3 .2]);

ylabel(‘Amplitude’);xlabel(‘time index n’);

subplot(2,2,4)

shiftn = n+2;plot(shiftn, fn)

title(‘f(n-2) vs. n’);

ylabel(‘Amplitude’);xlabel(‘time index n’);

axis([0 5 -.5 2.5]);

disp(‘*********** RESULTS ARE : ************************’)

Energy _ fn = sum(fnsquare)

disp(‘ ’)

Power _ fn = Energyfn/length(n) % asuming, f (n) is periodic T=20

disp(‘(in joules and watts)’)

disp(‘*************************************************’)

The script fi le f_ n is executed and the results are shown as follows and in Figure 1.57.

**************** RESULTS ARE:*******************

Energy _ fn =

34.8500

Power _ fn =

0.1734

(in joules and watts)

*************************************************

f(n) versus n

−f(n) versus n f(n−2) versus n

[f(n)]^2 versus n

2

1.5

0.5

0

0

−0.5

2.5

1.5

0.5

0

0

−0.5

1

2

− 1

−1.5

− 2

0 2 4

024

1

Amplitude

Amplitude Amplitude

Amplitude

4

3

2

1

0

024

time index n

12345

time index n

FIGURE 1.57

Plots of f(n), f(n)^2 , −f(n), and f(n − 2) of Example 1.8.