How to determine frequency components in a signal

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Elysi Cochin 2017-3-6

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https://ww2.mathworks.cn/matlabcentral/answers/328292-how-to-determine-frequency-components-in-a-signal

评论： Walter Roberson 2017-3-6

How to determine the different dominant frequency components in a signal (for the whole signal duration and for specific periods)? Signal is of dim (400 x 1)

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Walter Roberson 2017-3-6

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https://ww2.mathworks.cn/matlabcentral/answers/328292-how-to-determine-frequency-components-in-a-signal#answer_257437

See spectrogram()

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Elysi Cochin 2017-3-6

编辑：Elysi Cochin 2017-3-6

any example you can show me... i havent used it....

spectrogram(signal) and fft(signal), gives me a complex value? what does it mean? how can i relate it to time period

Walter Roberson 2017-3-6

在 MATLAB Online 中打开

mask = time >= beginning_of_period & time <= end_of_period;
selected_samples = samples(mask);
fft_of_selected = fft(selected_samples);

"spectrogram(signal), gives me a complex value?"

Yes. spectrogram does a series of discrete fourier transforms (fft). fft() of a real-valued signal is going to be complex except in the case that the signal is made up of pure sine tones that all started at the first sample. The complex portion of the entries express phase information.

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