🐛 Fix ideal_bandpass filter

[birajstha]

Fixes

Fixes numpy.linalg.LinAlgError: singular matrix error in #2225 by @shnizzedy
Fixes eigenvector centrality crash in in-progress #2230 by @shnizzedy

Description

This PR fixes a bug in the ideal_bandpass function where the frequency mask was incorrectly applied, which could cause the filter to fail or behave unexpectedly, especially for certain edge cases in bandpass frequency selection.

The issue was caused by an incorrect use of boolean logic (f_data[freq_mask is not True] = 0.0) which did not apply the mask elementwise. This has now been corrected to f_data[~freq_mask] = 0.0.

Technical details

Replaced

f_data[freq_mask is not True] = 0.0

with

f_data[~freq_mask] = 0.0

which applies the negation elementwise, as intended.

The FFT zero-padding and bandpass index calculation remain unchanged in terms of functionality. Variable naming was slightly improved for readability (e.g., nyquist_freq used instead of repeated sample_freq / 2.0).

Tests

Manually inspected non-zero outputs from this function.

Screenshots

Before fix

After fix

Checklist

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the develop branch of the repository.
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added tests for the changes I made (if applicable).
• I updated the changelog.
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no visible errors.

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[codecov]

Codecov Report

Attention: Patch coverage is 95.74468% with 2 lines in your changes missing coverage. Please review.

Project coverage is 28.3%. Comparing base (fde14a5) to head (bae5da4).
Report is 10 commits behind head on develop.

Files with missing lines	Patch %	Lines
CPAC/nuisance/bandpass.py	85.7%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #2237     +/-   ##
=========================================
+ Coverage     28.1%   28.3%   +0.2%     
=========================================
  Files          230     230             
  Lines        25941   25978     +37     
  Branches      4081    4081             
=========================================
+ Hits          7299    7353     +54     
+ Misses       18013   17996     -17     
  Partials       629     629             

Files with missing lines	Coverage Δ
CPAC/nuisance/tests/test_bandpass.py	100.0% <100.0%> (ø)
CPAC/nuisance/bandpass.py	42.7% <85.7%> (+21.8%)	⬆️

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[shnizzedy]

This is great. And it resolved the crash I was hitting in #2230!

We could add a parameterization where LowCutoff > nyquist_freq and HighCutoff > nyquist_freq or HighCutoff is None(¹) and this other parameterization and get full coverage of this PR, but I also think it's good to go as-is.

Footnotes

1. Is it conceptually correct that those are both > nyquist_freq? I see it was already that way, and I don't know enough about filtering terminology to know if that's intended ↩

[birajstha]

@shnizzedy , Yes nyquist_freq is the hard cutoff, we do not want anything above this frequency.