Signal Processing Toolbox

Median Filtering

The function medfilt1 implements one-dimensional median filtering, a nonlinear technique that applies a sliding window to a sequence. The median filter replaces the center value in the window with the median value of all the points within the window [5]. In computing this median, medfilt1 assumes zeros beyond the input points.

When the number of elements n in the window is even, medfilt1 sorts the numbers, then takes the average of the (n-1)/2 and (n-1)/2 + 1 elements.

Two simple examples with fourth- and third-order median filters are

• medfilt1([4 3 5 2 8 9 1],4)
  ans =
      1.500 3.500 3.500 4.000 6.500 5.000 4.500
  medfilt1([4 3 5 2 8 9 1],3)
  ans =
       3     4     3     5     8     8     1
  

See the medfilt2 function in the Image Processing Toolbox documentation for information on two-dimensional median filtering.

FFT-Based Time-Frequency Analysis

Communications Applications

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