%% fftperformance
%%% define signal, sample rate, sample domain
N = 1024;
t = (0:1:(N-1));
dft = t.^2;
CT  = t.*log(1+t);

figure(1)
clf
plot(t,dft,t,CT);
title('DFT and FFT performance, powers of 2'); 
xlabel('data size N');
ylabel('number of flops');
axis tight

disp('press a key');
pause

ops = [];
for n = 1:N 
   flops(0);
   fft(rand(1,n)); 
   ops = [ops,flops];
end 

figure(2)
clf
plot(1:N,ops);
title('FFT performance, dependence on N'); 
xlabel('data size N');
ylabel('number of flops');
axis tight