npts = 2500
delt = 0.001;
t = (1:npts)*delt;
s = sin(2*pi*7*t); % sine wave, freq = 7 Hz.
[xhat a b] = DFT(s);
delf = 1/delt;
f = (0:(length(t)/2-1)) * delf / npts;
plot(f, a.^2+b.^2);



A = [68	46	47	49	55	56	62	55;
179	176	186	178	65	9	10	11;
219	227	227	236	46	17	9	17;
218	217	219	230	42	20	20	20;
218	221	217	211	20	22	23	24;
226	223	223	125	17	19	21	22;
223	228	231	33	18	17	20	18;
225	231	202	26	20	17	21	19];
Entropy(A-127)