% example Bode plot
bode(tf([1], [1,2,3]));

% note if you plot it yourself you must convert the magnitude
% and the frequency axis limits will be different
% compare the following to the above

[mag, phase, w] = bode(tf([1], [1,2,3]));

figure
subplot(2,1,1)
semilogx(w,20*squeeze(log10(mag)))
subplot(2,1,2)
semilogx(w,squeeze(phase))
