quantization Noise Spectrum analysis.Mybe there are bug over there

quantizationNoiseSpectrum.m

close all 
clear all
% for n=1:10:10000
fsample=1424424;
f=fsample/1020.32;
A=1;

lens=2^20;
N=15;

theta=(2*pi*f/fsample*[1:lens]);
Sig=sin(theta);

quantizedSig=round(2^(N-1)*Sig);
% plot([Sig',quantizedSig']);
% plot(2^(N-1)*Sig(1:10000)-quantizedSig(1:10000));
% figure();
% hist(2^(N-1)*Sig(1:10000)-quantizedSig(1:10000),100);
h2=figure(1);
subplot(211)
plot(2^(N-1)*Sig(1:10000)-quantizedSig(1:10000));
title('量化误差');
subplot(212);
fftvar=abs(fft(2^(N-1)*Sig-quantizedSig).^2);
f=linspace(0,fsample,length(fftvar));
plot(f,fftvar);
title('量化误差功率谱');
filename=strcat('b',num2str(1),'.png');
saveas(h2,filename);
% disp('信号功率：');
% Ps=mean((2^(N-1)*Sig).^2);
% disp(Ps);
% disp('量化噪声功率：');
% Pn=mean((2^(N-1)*Sig-quantizedSig).^2);
% disp(Pn);
% disp('信噪比:');
% disp(10*log(Ps/Pn));
% disp('理论信噪比');
% disp(1.76+6.02*N);
% filename=strcat('b',num2str(n),'.png');
% saveas(h2,filename);
% end