Hi,
For plotting the function mentioned in the question you may use square wave as it will replicate your requirements. I have written an example below which plots the function in range [-16π,16π]. You may find it helpful.
% This particular t will plot 16 cycles
% t can be changed accordingly for plotting particular number of cycles
t = -16*pi:0.02:16*pi;
x = 3*square(t); % Period of the wave is 2*pi
x = x.*(x>=0); % converting negative cycle to zero as per function requirement
plot(t/pi,x); % Plotting t/pi for better understanding
xticks(-16:16);
xlabel('t / \pi')
ylim([-1,4]);
xlim([-17,17]);
