[求助]请指教下面程序哪里不对

[pslpsl]

 
clear all
fs=200;
nfft=200;
order=20;
t=0:1/fs:1;
f1=20;
x=sin(2*pi*f1*t)+sqrt(0.1)*randn(size(t));
order=floor(length(x)/5);
[p,f]=pburg(x,order,nfft,fs);
pmax=max(p);
p=p/pmax;
p1=10*log10(p);
plot(f,p1)
grid on;
xlabel('Frequency(Hz)');
ylabel('相对功率谱密度(dB/Hz)');
title('Burg PSD Estimate');
ymin_psd=min(p1)-1;
ymax_psd=max(p1)+1;
axis([0 fs/2 ymin_psd ymax_psd]);