Comparing the curves of the graphs

Question

ivko ivkovic 2022-2-21

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1655180-comparing-the-curves-of-the-graphs

评论： Image Analyst 2022-2-27

在 MATLAB Online 中打开

Comparing the curves

>> NFFT = 2^nextpow2(L); % Next power of 2 from length of y
Y = fft(y,NFFT)/L;
f = Fs/2*linspace(0,1,NFFT/2+1);
% Plot single-sided amplitude spectrum.
plot(f,2*abs(Y(1:NFFT/2+1)))
title('Single-Sided Amplitude Spectrum of y(t)')
xlabel('Frequency (Hz)')
ylabel('|Y(f)|')
>> Fs = 1000; % Sampling frequency
T = 1/Fs; % Sample time
L = 1000; % Length of signal
t = (0:L-1)*T; % Time vector
% Sum of a 50 Hz sinusoid and a 120 Hz sinusoid
x = 0.7*sin(2*pi*50*t) + sin(2*pi*120*t);
y = x + 2*randn(size(t)); % Sinusoids plus noise
plot(Fs*t(1:50),y(1:50))
title('Signal Corrupted with Zero-Mean Random Noise')
xlabel('time (milliseconds)')
>>

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Answer 1

Image Analyst 2022-2-21

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1655180-comparing-the-curves-of-the-graphs#answer_901340

The spectrum (left plot) shows a spike at 50 and 120 Hz. I'd never know that there is monotone noise at those exact frequencies just by looking at the time domain plot on the right. So I'd say the frequency domain plot is most informative in this particular case.