MATLAB: Detecting samples greater than a threshold and grouping.

detectiongroupingImage Processing Toolboxthreshold

Hi all,
Lets say we have a vector: A = [1 2 3 5 2 3 5 2 5 3 10 8 9 11 14 1 4 3 3 4 5 3 2 3 4 5 6 4 2 2 3 4 5 6 6 2 2 3 4 11 23 12 56 23 12 34 12 1 3 4 1 2 3 4 5 ];
In the vector, I have applied a threshold of A>5 for detection of any samples greater than 5. So I detect all the bold samples.
However, as a second step, I want to group these samples. As in, first bold set goes to group 1 and second bold set goes to group 2 (All the consecutive samples goes to same group). How can I do it in Matlab in a way that their original indices in vector A are preserved?
Kind Regards
Anum

Best Answer

What you want is bwlabel(), in the Image Processing Toolbox:
A = [1 2 3 5 2 3  5  2 5 3 10 8 9 11 14 1 4 3  3 4 5 3 2 3 4 5 6 4 2 2 3 4 5 6 6  2 2 3 4 11 23 12 56 23 12 34 12 1 3  4  1 2 3 4 5 ]; 
[groups, numGroups] = bwlabel(A > 5)
groups =
Columns 1 through 27
0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 2
Columns 28 through 54
0 0 0 0 0 0 3 3 0 0 0 0 4 4 4 4 4 4 4 4 0 0 0 0 0 0 0
Column 55
0
numGroups =
4
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