% Set up x[n] for N=8
N = 8;
n = 0 : N-1
x = (-1.0).^n;

% 8-point DFT for N=8
dft8 = fft(x, 8);
stem(abs(dft8));

% 9-point DTF for N=8
figure(2);
dft9 = fft(x, 9);
stem(abs(dft9));