How to apply a appropriate sampleing frequency and cut off frquency for a low pass filter

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nam bui 2021-2-12

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评论： Star Strider 2021-2-12

hello, if you have a set of raw data like this how can you set a appropriate sampling frequency and cut off frequency?

Because I know that the table above provided a sampling frequency of Fs = 0.01 so I'm wondering if you change the value of Fs in the code, will it affect the filtered plot?

Thank you

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Answer 1

Star Strider 2021-2-12

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‘Because I know that the table above provided a sampling frequency of Fs = 0.01 ...’

That is not the sampling frequency. It is the sampling interval, and should actually be:

Ts = 0.01;                                                  % Sampling Interval
Fs = 1/Ts;                                                  % Sampling Frequency
Fn = Fs/2;                                                  % Nyquist Frequency

The sampling interval and sampling frequency cannot be changed, and produce meaningful output. The filter must use the information provided in the signal.

The cutoff (passband) frequency must be greater than 0 and less than the Nyquist frequency. What it is depends on what you want the filter to do.