I was reading a research paper which deals with gait monitoring using android accelerometer sensor data values at 50 Hz. It uses a low pass filter to filter the noise with a cut-off frequency of 8 Hz.
This is the pseudo code for Low Pass Filter i got from wikipedia:
for i from 1 to n
y[i] := y[i-1] + α * (x[i] - y[i-1])
how should i set the value of α so that this works at 8 Hz.
You can use this formula to calculate alpha.
α := dt / (T + dt)
T = 1/fc, dt = sampling interval
In your case
dt = 1/50Hz = 0.02 sec
msT = 1/fc = 1/8 = 0.125 sec
msα = 0.02/(0.02 + 0.125) = 0.137931034
Take a look at this link for further explanation
EDIT:
Units are updated from msec to sec. Thanks to @IR_IR for pointing out this mistake.