evaluate rising edge sample of a signal

Good evening, I'm trying to evaluate the rising edge samples of the signal,for each local maximum and minimum, that I have highlighted in red,in the Figure, and put them in a vector. I tried with "islocalmin" to locate the minimum but it wasn't able to locate anything.

Can you give me some advices.

[Turlough Hughes]

Can you share the data?

[alessandro mutasci]

yes, the vector is attached, I use this for local maximum, [pks, locs] = findpeaks(Mf, 'MinPeakDistance', 50, 'MinPeakHeight', 1); but for the evaluation of the position and the value of the local minimun, so i can do the difference for the 2 positions to evaluate the rising edge sample signal, i don't know how to do it.

I tried [min, locsm] = islocalmin(Mf, 'MinSeparation', 50) and [min, locsm] = islocalmin(Mf, 'FlatSelection', 'last'); but stil nothing.

Answer 1

[Turlough Hughes]

Is it just the local minima you're having trouble with?

Edit:

The rising edge is found where the slope of the original data is positive. You can get the start and end of these regions where the slope is positive and they also correspond to the min and max of the rising edge:

load(websave('mf.mat','https://uk.mathworks.com/matlabcentral/answers/uploaded_files/720144/mf.mat'))

dMf  = [0; diff(smooth(Mf,'moving',5))];

figure('WindowState','Maximized')

subplot(2,1,1)
plot(Mf); 
xlim([1 numel(Mf)])
title('Signal')
set(gca,'fontSize',12)

subplot(2,1,2)
plot(dMf)
xlim([1 numel(Mf)])
title('Slope of Signal')
set(gca,'fontSize',12)


subplot(2,1,1)
idx = dMf > 0; % index for rising edges (where slope > 0).
hold on
plot(find(idx),Mf(idx),'ok','LineWidth',2,'MarkerSize',4)

% Get start and end indices for rising edges.
iStart = find(diff(idx) ==  1) + 1;
iEnd = find(diff(idx) == -1) + 1;

if idx(1) == 1
    iStart(1) = [1; iStart];
end

if idx(end) == 1
    iEnd = [iEnd; numel(idx)];
end

idel = iEnd - iStart <= 20; % threshold size for a group

iEnd(idel) = [];
iStart(idel) = [];

plot(iStart,Mf(iStart),'or','MarkerFaceColor','r','MarkerSize',10)
plot(iEnd,Mf(iEnd),'sr','MarkerFaceColor','r','MarkerSize',10)

legend('Original data','Rising edge','Min','Max','Location','NorthWest')

[alessandro mutasci]

Yes... I tried it, but it's not working.. when I send that command in the command window, nothing shows up, and the idx variable is all 0..

[alessandro mutasci]

thank you very much! but now I have a question regarding your procedure. Now for the evaluation of the rising edge samples, I need to do it "by hand", not with matlab? or am I mistaken? because when there are only 3 edges it's ok, but if I have to do it for 100 edges, there is a problem... I thougth there could be an optimal way

[Turlough Hughes]

See edit above

[alessandro mutasci]

yes! it's working! thank you so much!

[Turlough Hughes]

Glad we got there. If you're happy with that then can you accept the answer.