why my dB plot doesn't seem right?

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Xiaolong wu
Xiaolong wu el 23 de Nov. de 2020
Comentada: Mathieu NOE el 24 de Nov. de 2020
Dear, I have a very simple signal, now I want to plot it. It seems all make sense when I plot it use linear scale. But I got very strange plot when I plot in log scale. code below:
%% test data
fs = 1000;
t = 0:1/fs:5-1/fs;
x = cos(2*pi*50*t)+cos(2*pi*100*t);
%plot(t,x)
%plotChannelSpectral(x);
[psd,f] = pwelch(x,500,200,500,1000);
plot(f,(psd)); % this one makes sense
figure;
plot(f,10*log10(psd)); %this just doesn't make sense
Should it be strght line?
And I don't know when should I use log scale and when should I use linear. For this instance, linear is very good, but log is not.
Thanks in advance.
  5 comentarios
Xiaolong wu
Xiaolong wu el 24 de Nov. de 2020
Thanks, I will try the bode plot definitely.
How am I supose to accept the answer, I remember there is a accept answer button?
Mathieu NOE
Mathieu NOE el 24 de Nov. de 2020
Make sure you are logged in.
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