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Marking the peak of a plot automatically without having to click on it

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Hi,
Is it possible to mark the peak of a plot automatically with a command without having to to mark on each plot.

Accepted Answer

Star Strider
Star Strider on 29 Aug 2012
Edited: Star Strider on 29 Aug 2012
If you have the Signal Processing Toobox, I suggest the findpeaks function with two outputs so that you get the value of the function at the peak as well as the index of your x-variable at which the peak occurs.
For example:
[Peak, PeakIdx] = findpeaks(Y);
and the label would then be:
text(x(PeakIdx), Peak, sprintf('Peak = %6.3f', Peak));
using the text command.
To illustrate:
X = [0:0.1:pi]';
Y = sin(X);
[Peak, PeakIdx] = findpeaks(Y);
figure(1)
plot(X, Y)
text(X(PeakIdx), Peak, sprintf('Peak = %6.3f', Peak))
  1 Comment
Kiki
Kiki on 29 Mar 2016
Hi
What if I have multiple peaks and I want the apply the label respectively? How should I write the text command?
Thank you!

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More Answers (3)

Wayne King
Wayne King on 29 Aug 2012
Do you know the value of the peak?, then yes, it's easy.
x = randn(100,1);
[val,I] = max(x);
plot(x); hold on;
plot(I,val,'r^','markerfacecolor',[1 0 0])
  7 Comments

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Ilham Hardy
Ilham Hardy on 29 Aug 2012
  4 Comments

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