How could I do a summation of (y) so I can create a signal that goes from 0 to 30 sec repeating (y) every 3 seconds in a graph.

A = 1.15;

t = linspace(-2, 1, 1000);

a = exp(-0.5*t);

y = A*a.*(sin(2*pi*3*t)) .* (ustep(t+2)-ustep(t));

figure

plot(t, y, 'LineWidth', 2)

xlabel('t');

ylabel('y');

title('L2E2');

grid on;

Answer 1

[Paul]

Maybe this is the goal? Note that I modified the definition of y to make it in line with what I assumed the question means.

A = 1.15;
a = @(t) exp(-0.5*t);
ustep = @(t) t>=0;
y = @(t) A*a(t).*(sin(2*pi*3*t)) .* (ustep(t) - ustep(t-2)); % changed from original code
t = -3:.01:3;
figure;
plot(t,y(t))

t = 0:.01:30;
plot(t,y(mod(t,3)))