15.2.11  Apply a moving average filter to a signal: moving_average

The moving_average command applies a moving average to a sample.

• moving_average takes two arguments:
  • A, an array of numeric values representing a sampled signal.
  • n, a positive integer n.
• moving_average(A,n) returns an array B obtained by applying a moving average filter of length n to A. The elements of B are defined by

  B[i]=

  1 n

  n−1 ∑ j=0

  A[i+j]

  for i=0,1,…,L−n, where L is the length of A.

Moving average filters are fast and useful for smoothing time-encoded signals.

Examples.

• Input:

  snd:=soundsec(2):

  noise:=randvector(length(snd),normald,0,0.05):;

  data:=0.5*threshold(3*sin(2*pi*220*snd),[-1.0,1.0])+noise:;

  plotwav(createwav(data),range=[1000,1500])

  Output:
  
• Input:

  fdata:=moving_average(data,25):;

  plotwav(createwav(fdata),range=[1000,1500])

  Output: