Issue with locating end of poorly defined peak

Hi folks,

I have several graphs that look similar to the one attached. I am trying to formalise a general approach to finding the location of the start and end of each peak. The start is somewhat easy (using find, and the peak position can be found using max), since the graph starts from 0 (I am interested only in the second entry onwards).

However, the end is really tricky as it never quite gets to zero. I have tried using findpeaks, and also myEnd = find(iso(myPeakLoc:end, 1) > 1e-06); but to no avail.

Can someone advise me on an alternative route please?

[Mathieu NOE]

hello

can you share your code as well (not only the data) ?

tx

Answer 1

[Mathieu NOE]

hello again

tried this - does it help ?

load('iso.mat')

curve = 10; % which curve do you want to plot ? 
data = percent_iso(2:end,curve);

% max point 
[maxval,maxind] = max(data);

% start point = find first point above 0.1% of max value
[startind] = find(data>0.001*maxval,1,'first');
startval = data(startind);

% stop point= find first point below 0.1% of max value past the peak
[endind] = find(data(maxind:end)<0.001*maxval,1,'first');
endind = endind + maxind;
endval = data(endind);

plot(data,'DisplayName','percent_iso')
hold on
plot(maxind,maxval,'dr',startind,startval,'dg',endind,endval,'dk');
hold off
legend('data','max','start','end');

[Teshan Rezel]

@Mathieu NOE this is perfect, thank you!

[Mathieu NOE]

as always, my pleasure !