Designs a 2nd-order Butterworth bandstop filter centred at freq Hz with
bandwidth bandwidth_hz and applies it zero-phase using
gsignal::filtfilt(). Because the filter has only ~9 coefficients, it is
safe to use on long recordings without memory issues.
Usage
notch_filter(signal, sr, freq, bandwidth_hz = 2, harmonics = TRUE)
Arguments
- signal
Numeric vector.
- sr
Numeric. Sampling rate in Hz.
- freq
Numeric. Centre frequency in Hz (e.g. 50 or 60).
- bandwidth_hz
Numeric. Full bandwidth of the notch in Hz. Default 2.
- harmonics
Logical. Also notch harmonics (2×, 3×, ...) below
Nyquist − 5 Hz. Default TRUE.
Value
Filtered numeric vector, same length as signal.
Details
By default also applies the filter at all harmonics of freq below the
Nyquist limit, which is the standard approach for powerline noise removal.
Examples
if (FALSE) { # \dontrun{
clean <- notch_filter(eeg_signal, sr = 256, freq = 50)
clean <- notch_filter(eeg_signal, sr = 256, freq = 60, harmonics = FALSE)
} # }
