fix precision and recall calculations

[cmmartin]

Fixes #323

Checklist

• My branch is up-to-date with development branch.
• Everything works and tested on latest stable Rust.
• Coverage and Linting have been applied

Current behaviour

• recall
  • binary case calculates precision instead of recall due to incorrect false negative counting
  • multiclass case computes accuracy (total correct / total) instead of macro-averaged recall
• precision
  • binary case calculates recall instead of precision due to incorrect false positive counting
  • multiclass case computes accuracy instead of macro-averaged precision

New expected behaviour

• recall
  • binary case correctly calculates recall
  • multiclass case computes macro-averaged recall instead of accuracy
  • handles zero-division edge case
• precision
  • binary case correctly calculates precision
  • multiclass case computes macro-averaged precision instead of accuracy
  • handles zero-division edge case

Change logs

[Mec-iS]

thanks a lot. I will review this on monday

[Mec-iS]

it would be nice to take the opportunity and make these statements to use approx where possible

[Mec-iS]

💯
Hope you will stick around!

[Mec-iS]

I will merge this and create a new release

[codecov]

Codecov Report

❌ Patch coverage is 51.42857% with 34 lines in your changes missing coverage. Please review.
✅ Project coverage is 45.68%. Comparing base (9fef05e) to head (6db62f2).
⚠️ Report is 11 commits behind head on development.

Files with missing lines	Patch %	Lines
src/metrics/precision.rs	51.35%	18 Missing ⚠️
src/metrics/recall.rs	51.51%	16 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           development     #338      +/-   ##
===============================================
+ Coverage        45.23%   45.68%   +0.44%     
===============================================
  Files               90       93       +3     
  Lines             7775     8034     +259     
===============================================
+ Hits              3517     3670     +153     
- Misses            4258     4364     +106     

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