Filters

Filters

butter_bandpass_filter(data, pass_freq, fs, order=5) staticmethod

Basic bandpass (notch) butterworth filter.
:param data: input data.
:param pass_freq: the tuple of (low, high) band frequencies.
:param fs: sampling frequency.

Source code in site-packages/cmtj/utils/filters.py

@staticmethod
def butter_bandpass_filter(data: np.ndarray,
                           pass_freq: Tuple[float, float],
                           fs: float,
                           order: int = 5):
    """
    Basic bandpass (notch) butterworth filter.  
    :param data: input data.  
    :param pass_freq: the tuple of (low, high) band frequencies.  
    :param fs: sampling frequency.
    """
    # Nyquist is half of the sampling freq
    nyq = 0.5 * fs
    if isinstance(pass_freq, float):
        if pass_freq == 0:
            pass_freq = 0.1
            try:
                b, a = butter(order,
                              [0.9 * pass_freq / nyq, pass_freq / nyq],
                              btype='bandpass',
                              analog=False)
            except ValueError:
                print(fs, pass_freq, nyq, 0.9 * pass_freq / nyq,
                      pass_freq / nyq)
                raise ValueError("Error in filtering")
    elif isinstance(pass_freq, tuple):
        b, a = butter(order, [pass_freq[0], pass_freq[1]],
                      btype='bandpass',
                      analog=False)
    y = lfilter(b, a, data, zi=None)
    return y

butter_lowpass_filter(data, cutoff, fs, order=5) staticmethod

Low pass digital filter.
:param data: data to be filtered.
:param cutoff: cutoff frequency of the filter.
:param fs: sampling frequency.
:param order: order of the filter.

Source code in site-packages/cmtj/utils/filters.py

@staticmethod
def butter_lowpass_filter(data: np.ndarray,
                          cutoff: float,
                          fs: float,
                          order: int = 5):
    """
    Low pass digital filter.  
    :param data: data to be filtered.  
    :param cutoff: cutoff frequency of the filter.   
    :param fs: sampling frequency.  
    :param order: order of the filter.  
    """
    nyq = 0.5 * fs
    normal_cutoff = cutoff / nyq
    b, a = butter(order, normal_cutoff, btype='low', analog=False)
    y = lfilter(b, a, data, zi=None)
    return y