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Feature enhancement: local maxima


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Next: Data reduction: histograms Up: No Title Previous: Feature enhancement: normalizing

Feature enhancement: local maxima

In some applications, the presence of a `bump' in a signal may be more significant than its size. Then, it is imperative to display a local maximum, say, of the wavelet map by factoring out its magnitude, giving equal emphasis to molehills and mountains. The following algorithm has been implemented for generate Fig. 25:

  1. identify a realistic size of an event on the wavelet map; for example, a rectangular box one-duration wide and allowing for limited ratio of durations in height, has been used.
  2. identify all local maxima by placing a box around them and verifying that no larger values occur within the box.
  3. within each box, normalize the values of the map by the local maximum.
  4. threshold what is left to show the vicinity of each maximum.
The result of these operations is shown below for the intermittent signal used in previous sections; a more complicated example was used in Fig.1.


Figure 25: Local maxima of g2-energy map.


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Jacques Lewalle
Mon Nov 13 10:51:25 EST 1995