how i can found the region of absolute stability ?

 n=0:30:180
h=((768 *cos((1/2)*n) + 96* cos(n) - 864) ./ (40*cos (1/2*n)+ 2*cos(n)+ 102))
figure
plot(n,h, 'b*-', 'LineWidth', 2)
grid on;
xlabel('n', 'FontSize', 20);
ylabel('h', 'FontSize', 20);

[dpb]

Explain???

Answer 1

[Image Analyst]

Because you're using / (array division) instead of ./ (element by element division). Try this:

n=0:30:180
h=((768 *cos((1/2)*n) + 96* cos(n) - 864) ./ (40*cos (1/2*n)+ 2*cos(n)+ 102))
figure
plot(n,h, 'b*-', 'LineWidth', 2)
grid on;
xlabel('n', 'FontSize', 20);
ylabel('h', 'FontSize', 20);

% Do it again with more resolution.
n = linspace(min(n), max(n), 1000);
h=((768 *cos((1/2)*n) + 96* cos(n) - 864) ./ (40*cos (1/2*n)+ 2*cos(n)+ 102))
hold on;
plot(n,h, 'r-', 'LineWidth', 2)
grid on;
xlabel('n', 'FontSize', 20);
ylabel('h', 'FontSize', 20);

[dpb]

+1 IA, my old eyes missed it (again)...

Answer 2

[sadeem alqarni]

how i can found the region of absolute stability ?

[Image Analyst]

How is this an "Answer" to your original question? Anyway, as you can see from my plot, it depends on how you define stable. The values are constantly changing so they're not stable, however the overall pattern seems pretty stable - it seems to oscillate pretty much the same way over the time period plotted.

[sadeem alqarni]

How do I do this plot,since my brograms above??

Answer 3

[sadeem alqarni]

[Image Analyst]

Is this your answer?

[sadeem alqarni]

no it is not my answer but i want know how i plot it?