FFT to represent Aliasing Problem

I have an sinusoidal signals ranging from 1 to 5 KHz and they are being sampled at 1500 Hz . I need to show the aliased spikes that fall in a LP filter of 1 kHz. Can fft be used ? I am trying a simple fft problem first but i cannot get the xasis correct. My code is :

 f = input ('Enter the analog frequencies: ');
 fs = input ('Enter the Sampling frequency: ');
 Ts = 1/fs;
 Ns = 512
 t = [0:Ts:Ts*(Ns-1)];
 x = sin(2*pi*f*t);
 X = fft(x,Ns)/Ns;
 xdft = fftshift(X);
 plot(abs(xdft))

Answer 1

[Rick Rosson]

fc = f;

df = fs/Ns;
f = -fs/2:df:fs/2-df;

plot(f,abs(xdft);