How to find first index before main peak in a signal ?

9 views (last 30 days)
Tomaszzz
Tomaszzz on 27 Jan 2022
Commented: Tomaszzz on 28 Jan 2022
Hi all,
I have a signal ( see figure an attached).
I want to identify loactions and values of indices circled bold black (first through before main through indicated by blue star)
I have values and locations of all the remaining indices (attached a b c and d).
I am able to identify indices circled red using the code below. I would assume I can modify it to get the indices in bold black but I fail to do this. Can you help please?
load 'signal'
load 'a' % load all through value
load 'b' % load all through location
load 'c' % load main through value
load 'd' % load main through location
counter = 0;
for i = 1:length(main_trough_location)
%finds end of movement cycle
index = all_trough_location > main_trough_location(i);
if sum(index)>0
counter = counter + 1;
end_location(counter) = all_trough_location(find(index,1));
end_value(counter) = all_trough_value(find(index, 1));
end
end
plot(thigh_orient_y,'k')
hold on
plot(all_trough_location,all_trough_value,'ko')
plot(main_trough_location,main_trough_value,'b*')
plot(end_location,end_value,'r*')
h = legend('signal',' all troughs','main troughs','end');

Accepted Answer

Simon Chan
Simon Chan on 27 Jan 2022
Suppose it is the minimum point before rising, you may try to find the first minumum point counting backwards from each peak.
load('signal.mat');
peak_location = find(islocalmax(thigh_orient_y,'MinProminence',40));
backward = arrayfun(@(x) diff(thigh_orient_y(x:-1:1)),peak_location,'UniformOutput',false);
num_back = cellfun(@(x) find(x>0,1,'first'),backward);
min_location = peak_location-num_back+1;
plot(thigh_orient_y);
hold on;
grid on;
plot(min_location,thigh_orient_y(min_location),'g*')
  4 Comments

Sign in to comment.

More Answers (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!