filter sampled excel data in matlab

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

Answer 1

[Arturo Moncada-Torres]

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).

[Arturo Moncada-Torres]

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]

ohh..im sorry i have made a mistake.

fs=16Hz ,fc=380Hz

i want to remove low frequency .

thanks in advance for ur valuable support

[Arturo Moncada-Torres]

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.