Peak Detection

It is often desirable to automatically detect peaks, particularly in a spectral envelope.

The peak is the location where the slope changes directions.

Figure 1: Peak Detection

% threshhold  
th = 0;                                     

% filter descending values
uslope = Ymag > [Ymag(1); Ymag(1:end-1)];

% filter ascending values
dslope = Ymag >= [Ymag(2:end); 1+Ymag(end)];

% only indeces at maxima retain non-zero value
Ymax = Ymag .* (Ymag > th) .* uslope .* dslope;

% peak indeces
maxixs = find(Ymax);