function pinpu_d(x,fs,cl)
%pinpu_sd频率对数显示,幅值转化dB
%x信号;
%fs采样频率;
%cl线型颜色
L=length(x);
N=L;
%N=2^nextpow2(L);
X=fft(x,N);
mag=abs(X(1:N))*2/L;
mag(1)=mag(1)/2;
f=fs*([1:N]-1)/N;
f=f(1:ceil(N/2))/10^3;
mag=mag(1:ceil(N/2));
maglg=20*log10(mag);
semilogx(f,maglg,cl);
fmax=fs/2/10^3;
xlim([0 fmax]);
%set(gca,'xtick',10.^[-2:floor(log10(fmax))]);
%set(gca,'xticklabel',{0.01 0.1 1 10});
xlabel('频率/kHz');ylabel('幅值/dB');title('对数幅频曲线');
grid on;
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