# Find the second signal points (x, y location) exactly the same place of the first signal peak (x, y) matlab

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Ganesh Naik on 27 Apr 2021
Commented: Mathieu NOE on 27 Apr 2021
Hi all, I have two signals where I find the negative peak of one signal and need to find the corresponding x,y points for the other signal. I was thinking of drawing a "vertical line" where the first signal peak is detected and then take the intersection point of the second signal. I think there are better straight forward methods to achieve this. In my example (please refer to the figure) x,y values are 413 and -6.18. I need to find the "y" value for the other signal (red signal) in the same location.
For your reference, I have attached the sample plot and the signal.
Kind regards

Mathieu NOE on 27 Apr 2021
hello
hope this helps you see function attached
x = Value(:,1);
y = Value(:,2);
t = 1:length(x);
threshold = min(y); %
[t0_pos,s0_pos,t0_neg,s0_neg]= crossing_V7(x,t,threshold,'linear'); % positive (pos) and negative (neg) slope crossing points
% ind => time index (samples)
% t0 => corresponding time (x) values
% s0 => corresponding function (y) values , obviously they must be equal to "threshold"
figure(1)
plot(t,x,t,y,t0_pos,s0_pos,'+r',t0_neg,s0_neg,'+g','linewidth',2,'markersize',12);grid on
legend('signal x','signal y','positive slope crossing points','negative slope crossing points');
% the point we are looking for is the last 'positive slope crossing points'
xx = t0_pos(end)
yy = threshold
Mathieu NOE on 27 Apr 2021
you're welcome
glad I could be of some help !

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