Designs a 4th-order Butterworth bandpass filter and applies it zero-phase
using gsignal::filtfilt(). Handles edge cases gracefully:
Usage
bandpass_filter(signal, sr, low_hz, high_hz)
Arguments
- signal
Numeric vector.
- sr
Numeric. Sampling rate in Hz.
- low_hz
Numeric. Low cutoff frequency in Hz. Use 0 or negative to
apply a low-pass filter only.
- high_hz
Numeric. High cutoff frequency in Hz.
Value
Filtered numeric vector, same length as signal.
Details
low_hz <= 0 → low-pass at high_hz
high_hz >= Nyquist → high-pass at low_hz
Otherwise → bandpass between low_hz and high_hz
The high_hz cutoff is clamped to 99 % of Nyquist to avoid instability.
Because this uses a short IIR filter, it is safe on long recordings.
Examples
if (FALSE) { # \dontrun{
# Standard EEG bandpass
filtered <- bandpass_filter(eeg_signal, sr = 256, low_hz = 0.3, high_hz = 35)
# High-pass only (baseline drift removal)
hp <- bandpass_filter(eeg_signal, sr = 256, low_hz = 0.1, high_hz = Inf)
} # }
