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Peak search algorithm
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peaksearch.xcodeproj
peaksearch
README.md

README.md

Peak Search Algorithm

This is a rather simple algorithm for finding the peaks in a set of points (think at a FFT spectrum), given as an array of value assumed to be regularly spaced along the abscissa. The result is the array of indexes of the peaks maxima.

Usage

Initialize a PeakSearch structure with the algorithm parameters:

struct PeakSearch ps;
ps.sigmas = 1.0;
ps.win_size = 4;
ps.data_s = 20;
ps.data_v = (float*) malloc(ps.data_s * sizeof(float));
data_t d[20] = {1,1,2,1,2,30,32,8,2,1,1,1,2,1,2,2,1,3,1,1};
ps.data_v = d;

Initialize a result vector (it will contain the peaks indexes); it will be resized as needed:

index_t *peaks = (index_t*) malloc(1 * sizeof(index_t));

Perform the search:

index_t count = search_peaks(&ps, &peaks);

Remember to free() the peaks array at the end:

free(peaks);

Rationale

The algorithm is based on a moving window (holding ps.win_size points) over the ps.data_v array, one element at a time.

At each iteration, the standard deviation of the moving window is compared to the overall standard deviation. If their ratio exceeds ps.sigmas, then it is assumed that the current window contains a peak.

For each consecutive set of windows containing a peak, the index of the maximum of the values is saved in the peaks array, which starts of size CHUNK_SIZE and then grows by multiples of this size when needed.

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