zero-phase filtering with scipy

ride_data.py

@@ -0,0 +1,53 @@
+import numpy as np
+from scipy.signal import butter, filtfilt
+
+sample_freq = 1.0
+cutoff_freq = 0.05
+order = 1
+
+
+def butter_lowpass_filter(data, cutoff, fs, order=5):
+    b, a = butter(order, cutoff, fs=fs, btype="low", analog=False)
+    y = filtfilt(b, a, data)
+    return y
+
+
+activity = GC.activity()
+power = np.array(activity["power"])
+seconds = np.array(activity["seconds"])
+
+GC.setChart(
+    title="Ride Data",
+    type=GC.CHART_LINE,
+    animate=False,
+    legpos=GC_ALIGN_TOP,
+    stack=False,
+)
+GC.addCurve(
+    name="Power",
+    x=seconds,
+    y=power,
+    xaxis="Time",
+    yaxis="Power",
+    color="yellow",
+    line=GC_LINE_SOLID,
+    symbol=GC_SYMBOL_NONE,
+    size=3,
+    opacity=100,
+    opengl=False,
+)
+GC.addCurve(
+    name="Power Smoothed",
+    x=seconds,
+    y=butter_lowpass_filter(power, cutoff_freq, sample_freq, order),
+    xaxis="Time",
+    yaxis="Power",
+    color="red",
+    line=GC_LINE_SOLID,
+    symbol=GC_SYMBOL_NONE,
+    size=3,
+    opacity=100,
+    opengl=False,
+)
+GC.setAxis("Power", min=0, max=800, type=GC.AXIS_CONTINUOUS)
+GC.setAxis('Time', type=GC.AXIS_TIME)