Fast Approximate Entropy

This function calculates Approximate Entropy (ApEn) of a time series data in a very efficient way.
Updated 20 Mar 2012

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Approximate Entropy (ApEn) is a popular tool in analysing the complexity of time series data especially in clinical research.

This function is a very simple and efficient implementation of ApEn, based on vectorization concept that improves speed tremendously over for-loop implementation.

It also contains a test code (foo.m) for generating a plot of ApEn of different simulated time series data, to help understand the usage. The test code generates a plot similar to that appearing in Ki H. Chon's 2009 paper in IEEE Eng in Med Biol, that discusses what r value we should use.

Cite As

Kijoon Lee (2024). Fast Approximate Entropy (, MATLAB Central File Exchange. Retrieved .

MATLAB Release Compatibility
Created with R2011b
Compatible with any release
Platform Compatibility
Windows macOS Linux
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Version Published Release Notes

The new version (Ver 1) has corrected a minor error in the definition of ApEn, and included another input argument tau for multi-scale ApEn calculation. See inside for details.