filter sampled excel data in matlab
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i have sampled data in excel and i want to filter it using high pass butterworth filter in matlab.i imported data from excel sheet .it is alredy sampaled.but how i filter it ?? plz help sampled freq = 44.1 khz, cutoff fre = 200 khz
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Arturo Moncada-Torres
2011-8-26
Filtering in MATLAB is something very easy. Take a look at the BUTTER and the FILTER commands. Here you will find everything you need. For example, let's suppose you have your original data in the variable "signal". On a quick thought:
fs = 44100; % Sampling frequency [Hz]
order = 2; % Order
fc = 200; % Cut-off frequency [Hz]
% Create the filter's numerator and denominator.
[num den] = butter(order, fc/(fs/2));
% Filter.
signalFiltered = filter(num, den, signal);
However, are you sure your values of fs and fc are correct? It is not logic to have a cut-off frequency larger than your Nyquist frequency (that is, half of the sampling frequency). In this case, it would not make sense having a cut-off frequency larger than 22.05 kHz. Notice how in my example, fc is 200 Hz (and NOT 200 kHz).
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Arturo Moncada-Torres
2011-8-29
Please see the edit for an example. Oh, and I cannot emphasize enough: are you sure you _fs_ and _fc_ are correct? As you have them now, they do not obey Nyquist/Shannon's sampling theorem.
Janaranjana Sampath
2011-8-29
Arturo Moncada-Torres
2011-8-30
The issue is the same, your fc is much higher than your fs. With a fs of 16 Hz, your maximum frequency analysis can be performed in the Nyquist frequency, that is in this case 8 Hz.
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