PeakFinder

Quickly finds local maxima (peaks) or minima (valleys) in a noisy signal.

Description

This function quickly finds local peaks or valleys (local extrema) in a noisy vector using a user defined magnitude threshold to determine if each peak is significantly larger (or smaller) than the data around it. The problem with the strictly derivative based peak finding algorithms is that if the signal is noisy many spurious peaks are found. However, more complex methods often take much longer for large data sets, require a large amount of user interaction, and still give highly variable results. This function attempts to use the alternating nature of the derivatives along with the user defined threshold to identify local maxima or minima in a vector quickly and robustly. The function is able to correctly identify the major peaks on a 1.5 million data point noisy sum of sinusoids in under a second as is shown in the example in the code comments.

Please don't hesitate to comment or contact me if you have suggestions about improvements that could be made to this function.

• MATLAB release: MATLAB 7.8 (R2009a)
• Other requirements: None

[Han]

Best code ever.

[Opalan]

 

[Brett Shoelson]

I've tried several approaches to detecting peaks in noisy data; this one worked best, and is exceptionally fast. Very nice work!

[Sandra]

How should I cite this code?

[Todd Karin]

 

[emma]

hi team

I am very new at this. How do I make this code find multiple peaks?

Thanks

[dolphin]

good

[Ershad Ahamed Chemmalasseri]

 

[mitra devkota]

Dear MATLAB users community,
I am a matlab newbie,I have x and y as vectors, I plotted them in MATLAB and now I need to detect the peaks and also find the corresponding peak locations. How can I use this code in my case?
Thanks in advance.
Mitra

[Willem]

Wang Feiran, to to find valleys you can use
peakfinder(data,[],[],-1)

[Wang Feiran]

 

[Wang Feiran]

Btw,the commend i was using is >>peakfinder(data) and i am a matlab newbie xD

[Wang Feiran]

Btw,how to use this code to detect valley?Thanks

[Wang Feiran]

Hello,i also have a problem with this code when i input the data under 1200 sampling frequency it doing well can detect all the peak points,but when i tried with other data under different sampling frequency sometimes it only can give me like half points some are missing,i don't know how to attach the image file,but can give me any help?

[Morteza Dehghani]

 

[raj]

Hello all, I have a problem with this code when my SNR is less 1.9 dB I CANT DETECT MY PEAKS OF INTEREST. What i want to know is it not possible to detect peaks at such noisy conditions ???

[Jan Heldal]

Joanne: That kind of error-message typically arises when Matlab does not know where the command resides (or when you misspelled it). Make sure that any m-file you wish to run are either in the current directory, and/or in your Matlab-path. If you have a separate folder for non-builtin m-files (such as peakfinder) that you wish to use, you can add that folder to the Matlab-path with the 'addpath' command, and put those m-files there.

[Joanne]

Sorry, I thought I'd written a longer message! I am also a MatLab newbie and am struggling to input the data and I get the above error message. Thanks if anyone can help. Jo

[Joanne]

I get the error:
Undefined function 'peakfinder' for input arguments of type
'double'.

[raj]

the code works well but some times it happens that peaks which are not required I mean after initializing a certain value for 'sel' the peaks which are not supposed to be detected (peaks created by noise) and sometimes they are not detected

[Michelle]

very quick and supportive response from the author. The output issue as listed above is due to my misunderstanding of the varargout. The other issue may also results from the Matlab setting rather than the code. Thank you, Nate.

[Michelle]

very useful code. However, it cannot output the PeakMag, but only the PeakLoc when I tried it recently. and after I used it several times with a vector, the acceptable number of the element seems to be locked. When used with other vectors having different numbers of elements,the extra elements cannot be shown in the plot and the output results. I hope someone can kindly explain this...

[Diana]

Hi, I find this routine very good and useful. However, for my problem I would need the start-end information about each peak so I could select just the peaks and work with them, How can I get this information?

Thanks in advance

[mohammad]

Really nice

[Robert]

 

[Estella Liu]

 

[Elisa]

Hi. I need to find peaks in a waveform and calculate the inter-pulse interval and the pulse rate from the position of the peaks. My data are sounds recorded at 24000Hz and saved in .wav files. This code seems to be doing exactly what I want but since I’m a matlab newbie I’m not quite sure how to input my data. Do you have any suggestions?
I hope this is the right place to post this message, otherwise I apologise.

[Nathanael Yoder]

Thanks for catching that Tim. You were exactly right, the redundancy is an artifact from when I preallocated the matrix for speed. However, I essentially replaced this statement with the leftMin variable which is why you got the same results. The end effect is that the second part of that conditional can simply be eliminated.

Thanks again for your help and an updated version with the addition of a user defined threshold should be available shortly.

[Tim]

I think I found a mistake in the code. Or at least something strange:

if foundPeak && (x(ii) > peakMag(end) || leftMin < peakMag(end)-thresh)

The second part, x(ii) > peakMag(end), is rather strange, since peakMag(end) will ALWAYS be equal to zero, since peakMag was preallocated with zeros. I guess this is a remainder from the time before you preallocated peakMag for speed.

I replaced the mistake with the following:

if foundPeak && (x(ii) > peakMag(cInd-1) || leftMin < peakMag(cInd-1)-thresh)

The strange thing is that the results luckily stay exactly the same, which is good but strange at the same time. There is probably some redundancy in the code.

In any case, your method was more or less what I was looking for. Just need to make some small adaptations to it for my purpose, of course leaving all credits to you. Thanks!

[David]

fantastic code, very effective even with highly noise data.

notably, it might be worth including an histogram based thresholding for a more optimal threshold selection.

[Nicholas]

Does anyone know of a comparable code that finds extrema in 2D or 3D data?

[antonio Acampora]

thanks

[Andres]

The bugs were fixed quickly. Thanks Nate!

[Andres]

I was happily using peakfinder until I had severe trouble with a dataset beginning with repeated values.
I've boiled it down to a short example:

t = [49 49 54 49 -57 46 -96 -10 39 0];
startI1 = 1;
[Loc1, Peak1] = peakfinder(t(startI1:end),20);
startI2 = 2;
[Loc2, Peak2] = peakfinder(t(startI2:end),20);

figure
plot(t,'b.-')
hold on
plot(Loc1-1+startI1,Peak1,'ro')
plot(Loc2-1+startI2,Peak2,'go')

Problems:
1) The first call returns a wrong result (Loc1 = 2, Peak1 = 49).
2) The second call returns all three peaks, but the last one appears twice (Loc2 = [2 5 8 8].', Peak2 = [54 46 39 39].').

I hope these issues can be fixed as peakfinder works promisingly fast.
A minor suggestion: if the input is a row vector the output should be a row vector, too.

Regards
Andres

[Morvan]