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Add single frequency bandpass to bwfilter #259

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merged 3 commits into from
Nov 16, 2021
Merged

Add single frequency bandpass to bwfilter #259

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6454b69
Add single frequency bandpass to bwfilter
jpa198 Nov 15, 2021
a043b55
Add bandstop and explicit lowpass
jpa198 Nov 16, 2021
fc39d6f
Give constants names
jpa198 Nov 16, 2021
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14 changes: 10 additions & 4 deletions qcore/timeseries.py
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Original file line number Diff line number Diff line change
Expand Up @@ -43,8 +43,10 @@
def bwfilter(data, dt, freq, band, match_powersb=True):
"""
data: np.array to filter
dt: timestep of data
freq: cutoff frequency
band: 'highpass' or 'lowpass'
band: One of {'highpass', 'lowpass', 'bandpass', 'bandstop'}
match_powersb: shift the target frequency so that the given frequency has no attenuation
"""
# power spectrum based LF/HF filter (shift cutoff)
# readable code commented, fast code uncommented
Expand All @@ -54,11 +56,15 @@ def bwfilter(data, dt, freq, band, match_powersb=True):
# x *= -1
# freq *= exp(x * math.log(sqrt(2.0) - 1.0))
nyq = 1.0 / (2.0 * dt)
highpass_shift = 0.8956803352330285
lowpass_shift = 1.1164697500474103
if match_powersb:
if band == "highpass":
freq *= 0.8956803352330285
else:
freq *= 1.1164697500474103
freq *= highpass_shift
elif band == "bandpass" or band == "bandstop":
freq = np.asarray((freq*highpass_shift, freq*lowpass_shift))
elif band == "lowpass":
freq *= lowpass_shift
return sosfiltfilt(
butter(4, freq / nyq, btype=band, output="sos"), data, padtype=None
)
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