I am not certain what you want to do.
Try this:
figure
subplot(3,1,1)
plot(t((t>=0) & (t<= 2*pi)),f(t((t>=0) & (t<= 2*pi))))
ylim([-1 1])
title("f(t)");
subplot(3,1,2)
plot(t((t>=-2*pi) & (t<=0)),-f(-t((t>=-2*pi) & (t<=0))))
ylim([-1 1])
title("-f(-t)");
subplot(3,1,3)
plot(t((t>=0) & (t<= 2*pi)),-f(t((t>=0) & (t<= 2*pi))+pi))
ylim([-1 1])
title("-f(t+T)");
hold off
Experiment to get the results you want. Remember that changes in the ‘t’ vector as the independent variable must be the same in the argument to ‘f’.
