Analyse cluster of extrema clusters

Hi all

I am analysing a signal and would like to know the (periodic) distance of my extrema. Is there any smart function which can cluster those based on the function value and then derive the average distance between maximum and minimum?

Taking all extrema into account doesn´t make sense due to the noises and different signal at start and beginning.

Thanks ahead

Answer 1

[prabhat kumar sharma]

Hi Florian,

I understand that you want to analyze signals and identify the periodic distance between extrema (maximum and minimum points) in a way that is robust against noise, you can use a combination of signal processing techniques and clustering. MATLAB provides a comprehensive set of tools for this purpose.

Here's a general steps that you might find useful:

1. Detrend and Smooth the Signal: This helps in reducing the impact of noise. You can use detrend to remove the linear trend and smoothdata for smoothing the signal.
2. Find Extrema: Use findpeaks to find maxima. For minima, you can invert the signal and use findpeaks again.
3. Clustering Extrema : If the extrema are clustered in groups (due to noise or signal characteristics), you might want to cluster them to find representative extrema. K-means clustering (kmeans) on the positions of these extrema can be useful, though it's optional and depends on your specific signal characteristics.

You can refer the documentations below:

detrend: https://www.mathworks.com/help/matlab/ref/detrend.html

smoothdata: https://www.mathworks.com/help/matlab/ref/smoothdata.html

findpeaks: https://www.mathworks.com/help/signal/ref/findpeaks.html

I hope it helps!