How can I find the value of vector for the local maximum and the nearest local minima (befor and after maximum value)?

Hi,

I have a vector array (e.g. 2 12 4 6 9 4 2 5 10 19 7 5 3 7 4) and I need to define the part of the vector with local maximum value and the neighbouring minima, located to the left and right of the maximum). In the above example it should be [2 5 10 19 7 5 3].how can I code that in matlab? any help please..

Thanks,

Answer 1

[Image Analyst]

Why does the 12 at element 2 not qualify as a local max? Do you have the Image Processing Toolbox, try imregionalmax(). If you have the Signal Processing Toolbox, try findpeaks on the signal and the inverted signal.

[Ashraf Afana]

Hi,

I have the imregionalmax() and I defined all the peaks on the vector and then I defined all the minima with imregionalmin(), but I still can't defined the part of the vector (array of all the values) that is limited to the minimums surrounding the maximum value of 19 in my example e.g.[2 5 10 19 7 5 3]. Sorry for that I’m not so experienced with matlab. Thanks,

[Image Analyst]

Try this:

m = [2 12 4 6 9 4 2 5 10 19 7 5 3 7 4]
regMax = imregionalmax(m)
regMin = imregionalmin(m)
% Find the 3rd peak
index3 = find(regMax, 3, 'first')
index3 = index3(end)
% Find out the mins on either side of that.
% Find the min locations
minLocations = find(regMin)-index3
% Find where the first one goes positive (right side)
rightIndex = minLocations(find(minLocations>0, 1, 'first'))+index3
% Get the left side:
leftIndex = minLocations(find(minLocations<=0, 1, 'last'))+index3
% Get the stretch from left min to right min on either side of the 19.
stretch = m(leftIndex:rightIndex)

[Ashraf Afana]

Thanks a lot, it works perfectly.

cheers