# Issue with locating end of poorly defined peak

조회 수: 1(최근 30일)
Teshan Rezel 2022년 6월 19일
댓글: Mathieu NOE 2022년 6월 22일
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.
##### 댓글 수: 1표시숨기기 없음
Mathieu NOE 2022년 6월 20일
hello
can you share your code as well (not only the data) ?
tx

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### 채택된 답변

Mathieu NOE 2022년 6월 20일
hello again
tried this - does it help ?
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');
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Mathieu NOE 2022년 6월 22일
as always, my pleasure !

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