MATLAB: Automatic Signal segmentation for feature extraction

classificationfeature extractionsignal processing

Hi,
Does anyone know how to do signal segmentation on the raw signal? I need to segment the raw signal into 8 different segments so that i can do feature extraction on individual segments.

Best Answer

Attach some signals so we can play with them.
Assuming the "tall" parts of the signal are not uniformly spaced (in which case you could extract them trivially with indexing at fixed indexes), then you need to find the center of the quiet parts. I'd start by thresholding the absolute value of the signal to find the low/quiet parts. You should have 9 of them, unless your tall signal parts hit the edge of your range. If you don't have 9, then I'd call imdilate repeatedly until you get exactly 9 quiet regions. Then I'd call regionprops() to get the centroid (middle index) of the quiet parts, and then I'd loop over the regions extracting the tall regions into cells. They need to be in cells because each region might have a different number of elements. Something like (untested)
quietParts = abs(signal) < threshold;
[~, numRegions] = bwlabel(quietParts);
while numRegions > 9
    quietParts = imdilate(quietParts, [1,1,1]);
    [~, numRegions] = bwlabel(quietParts);
end
% Now we should have the quiet parts.  Find the centroids.
props = regionprops(quietParts, 'Centroid');
% Extract each tall signal part into a cell
for k = 1 : length(props)-1
    index1 = round(props(k).Centroid;
    index2 = round(props(k+1).Centroid;
    individualSignals{k} = signal(index1:index2);
end
Note, the code above requires the Image Processing Toolbox.
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