included low pass filter in package and add to plot_data example

examples/viz/signal_filters.py

@@ -1,32 +1,5 @@
 """Signal filtering helpers for example force charts."""
 
-from __future__ import annotations
+from orisys.signal_processing import lowpass_filter
 
-import numpy as np
-from scipy.signal import butter, filtfilt
-
-def lowpass_filter(data, cutoff_hz=5, sample_rate_hz=30, order=2) -> np.ndarray:
-    """Zero-phase Butterworth low-pass filter for uniformly sampled 1-D data."""
-    y = np.asarray(data, dtype=np.float64)
-    if cutoff_hz == 0:
-        return y.copy()
-    if y.size == 0:
-        return y
-
-    nyquist = 0.5 * sample_rate_hz
-    if cutoff_hz < 0 or cutoff_hz >= nyquist:
-        raise ValueError(
-            f"cutoff_hz must be in (0, {nyquist}) for sample_rate_hz={sample_rate_hz}"
-        )
-
-    b, a = butter(order, cutoff_hz / nyquist, btype="low")
-    taplen = max(len(a), len(b))
-    # scipy.signal.filtfilt requires len(x) > padlen (default 3 * taplen for recent scipy).
-    padlen = 3 * taplen
-    if y.size <= padlen:
-        return y.copy()
-
-    try:
-        return filtfilt(b, a, y)
-    except ValueError:
-        return y.copy()
+__all__ = ["lowpass_filter"]