Exponential average filter without the TIirState structure. The function can be called to filter sample by sample. Initialize the State to 0 on the first call. Decay defines the decay from sample to sample and is initialized to 50% by default. With each new sample, the filter will take average from the 50% of the new sample and 50% of the previous average. The exponential average filter implements the following difference equation:
y[i] = 1/d * x[i] + (d-1)/d * y[i-1]
x.. input signal
y.. output signal
d.. Decay factor
In terms of percentage:
y[i] = a * x[i] + b * y[i-1] , a + b = 1
a*100 ... percent of the new data used.
b*100 ... percent of the old average used to compute the new average.
