Add validation tests for DFA scaling exponent

[Oberon245]

This PR adds validation tests for the existing Detrended Fluctuation Analysis (DFA) implementation in helpers.dfa.

The tests verify expected scaling behaviour using synthetic signals:

• White noise → α ≈ 0.5
• Brownian motion → α ≈ 1.5

Additional tests cover:

• behaviour on short time series
• determinism of output
• integration with the TimeSeries API

DFA follows the algorithm introduced in Peng et al. (1994), and these tests ensure expected scaling behavior is preserved.

[ThomasMBury]

Hi Robin,

Thank you very much for adding DFA to ewstools! This is a really nice addition that will be valuable for users. We could also consider adding a short Jupyter notebook tutorial to demonstrate how to use it.

Thanks again for the contribution - much appreciated.

Tom

[Oberon245]

Hi Tom, Thanks very much—I’m glad it’s a useful addition. I’d be happy to put together a short Jupyter notebook demonstrating DFA usage within ewstools. I can draft something that shows typical workflows and interpretation. Let me know if there’s anything specific you’d like included. Best, Robin

…

On Fri, Apr 3, 2026 at 4:23 PM Thomas Bury ***@***.***> wrote: *ThomasMBury* left a comment (ThomasMBury/ewstools#463) <#463 (comment)> Hi Robin, Thank you very much for adding DFA to ewstools! This is a really nice addition that will be valuable for users. We could also consider adding a short Jupyter notebook tutorial to demonstrate how to use it. Thanks again for the contribution - much appreciated. Tom — Reply to this email directly, view it on GitHub <#463 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AHAN3I3JTAOUH23DVXTC67T4UBBXHAVCNFSM6AAAAACW4I3CXWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DCOBVGU4TCMBQGM> . You are receiving this because you authored the thread.Message ID: ***@***.***>

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