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

Hi,

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

Answer 1

[Star Strider]

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))

[Kiki]

Hi

What if I have multiple peaks and I want the apply the label respectively? How should I write the text command?

Thank you!

Answer 2

[Wayne King]

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])

[Lisa Justin]

no i do not know the values of the peak, i want the value at the peak to also be visible. Same as using the data cursor on a plot directly. it a bunch of signals and i want to run a script on all, i would also like my script to mark the peaks automatically so i do not need to mark each plot before saving

[Tom]

are you looking for one single maximum value, or are you looking for local peaks (i.e. the peaks of a sine wave where there can be several per plot)?

[Lisa Justin]

one single maximum value

[Tom]

Then Wayne's code above should work fine.

[Lisa Justin]

But the value is not displayed on the plot with Wayne's code

[Tom]

It should be; can you provide some sample data?

[Ilham Hardy]

Below link is the 'how-to' display tooltip syntactically..

http://undocumentedmatlab.com/blog/controlling-plot-data-tips/

Happy reading,

Answer 3

[Ilham Hardy]

Possible,

see http://www.mathworks.ch/matlabcentral/fileexchange/25500-peakfinder

[Lisa Justin]

I also need the value at that peak to be displayed. Same as using the data cursor on a plot to mark points. but i want the data cursor to mark the peaks in my plot automatically so i do not need to mark it directly

[Jan]

Then use the output of the peakfinder and a simple TEXT command.

[Lisa Justin]

thanks, but what do you mean by simple TEXT command

[Jan]

See "help text" and "doc text".

Answer 4

[Sergio Yanez-Pagans]

You could use my MATLAB File Exchange function:

https://www.mathworks.com/matlabcentral/fileexchange/89491-peaks-and-dips

Hope you find this useful!