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"""
This module provides functions for filtering traces using digital (low/high/band)-pass and bandstop filters.
"""
from public import public
from scipy.signal import butter, lfilter
from typing import Union, Tuple
from .trace import Trace
def _filter_any(
trace: Trace,
sampling_frequency: int,
cutoff: Union[int, Tuple[int, int]],
band_type: str,
) -> Trace:
nyq = 0.5 * sampling_frequency
if not isinstance(cutoff, int):
b, a = butter(
6,
tuple(map(lambda x: x / nyq, cutoff)),
btype=band_type,
analog=False,
output="ba",
)
else:
b, a = butter(6, cutoff / nyq, btype=band_type, analog=False, output="ba")
return trace.with_samples(lfilter(b, a, trace.samples))
@public
def filter_lowpass(trace: Trace, sampling_frequency: int, cutoff: int) -> Trace:
"""
Apply a lowpass digital filter (Butterworth) to `trace`, given `sampling_frequency` and
`cutoff` frequency.
:param trace:
:param sampling_frequency:
:param cutoff:
:return:
"""
return _filter_any(trace, sampling_frequency, cutoff, "lowpass")
@public
def filter_highpass(trace: Trace, sampling_frequency: int, cutoff: int) -> Trace:
"""
Apply a highpass digital filter (Butterworth) to `trace`, given `sampling_frequency` and
`cutoff` frequency.
:param trace:
:param sampling_frequency:
:param cutoff:
:return:
"""
return _filter_any(trace, sampling_frequency, cutoff, "highpass")
@public
def filter_bandpass(
trace: Trace, sampling_frequency: int, low: int, high: int
) -> Trace:
"""
Apply a bandpass digital filter (Butterworth) to `trace`, given `sampling_frequency`, with the
passband from `low` to `high`.
:param trace:
:param sampling_frequency:
:param low:
:param high:
:return:
"""
return _filter_any(trace, sampling_frequency, (low, high), "bandpass")
@public
def filter_bandstop(
trace: Trace, sampling_frequency: int, low: int, high: int
) -> Trace:
"""
Apply a bandstop digital filter (Butterworth) to `trace`, given `sampling_frequency`, with the
stopband from `low` to `high`.
:param trace:
:param sampling_frequency:
:param low:
:param high:
:return:
"""
return _filter_any(trace, sampling_frequency, (low, high), "bandstop")
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