Original Code
The code that follows has a bug.
F0 =13; T0 =1/F0; Ts = 0.07; t = 0:Ts:13*T0; x = real(exp(j*(2*pi*F0*t-pi/2))); plot(t,x)
Problem with Original Code
The problem with the original code is that it cannot plot 13 cycles of the 13Hz sinusoid because the Time Step (Ts) value is much too large since the value of 1 cycle is .0769. Therefore the Time Step must be greatly reduced. Dividing the Time Step by 130 gives us 13 cycles on the plot.
Code with Bug Fixed
F0 =13; T0 =1/F0; Ts = 0.07/130; t = 0:Ts:13*T0; x = real(exp(j*(2*pi*F0*t-pi/2))); plot(t,x)