Code Quality Improvements: Logging, Constants, Docs & Cleanup

[cnicholas]

Summary

This PR addresses Issues #12, #14, #16, and #18, implementing four targeted code quality improvements that enhance maintainability, professionalism, and developer experience.

Changes

🧹 Issue #12: Remove Duplicate Utility Functions (HIGH PRIORITY)

Problem: Five utility functions were duplicated between analysis_dataset.py and objects.py, creating a maintenance burden and risk of divergence.

Solution:

• ✅ Removed 69 lines of duplicate code from analysis_dataset.py
  • calculate_limits() - Control limit calculations
  • c4() - Bias constant for Xbar/S charts
  • b3(), b4() - S chart limit multipliers
  • detect_beyond_limits() - Point detection logic
• ✅ Single source of truth maintained in objects.py
• ✅ All code now uses obj.calculate_limits() pattern

Impact: Eliminates risk of bugs being fixed in one place but not the other

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📝 Issue #14: Replace print() with Proper Logging (MEDIUM PRIORITY)

Problem: 33+ print() statements scattered throughout production code made debugging unprofessional and uncontrollable.

Solution:

• ✅ Added module-level logger: logger = logging.getLogger(__name__)
• ✅ Replaced all print() statements with appropriate logging levels:
  • logger.debug() - 25 instances for data inspection and flow tracing
  • logger.info() - 5 instances for important operations (e.g., zero-centering)
  • logger.warning() - 3 instances for limitations and edge cases

Examples:

# Before
print(f'\nIn calculate statistics XbarS...')
print(f'zero-centering data')

# After
logger.debug('In calculate statistics XbarS')
logger.info('Zero-centering data')

Benefits:

• Professional, configurable output
• No performance impact when logging disabled
• Better production debugging

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🔢 Issue #16: Replace Magic Numbers with Named Constants (MEDIUM PRIORITY)

Problem: Statistical constants (2.66, 3.268, 3) appeared throughout code with no explanation of their origin or purpose.

Solution:

• ✅ Added well-documented constants in objects.py:

# Statistical constants based on SPC theory
SIGMA_MULTIPLIER = 3                # Standard 3-sigma control limits
IMR_LIMIT_MULTIPLIER = 2.66         # E2 constant (n=2 moving range)
R_UPPER_LIMIT_MULTIPLIER = 3.268    # D4 constant (n=2 range chart)

• ✅ Updated 8 locations using magic numbers:
  • calculate_limits() - Xbar, IMR, R calculations
  • b3(), b4() - S chart calculations

Before:

lcl = mean + (-1.0 * (2.66 * mR))  # What is 2.66?
ucl = mR * 3.268                   # Where does 3.268 come from?

After:

lcl = mean + (-1.0 * (IMR_LIMIT_MULTIPLIER * mR))  # Clear meaning
ucl = mR * R_UPPER_LIMIT_MULTIPLIER                # Self-documenting

Benefits:

• Self-documenting code
• Easy to verify against statistical references
• Single point of modification

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📚 Issue #18: Document Sampling Design State Logic (MEDIUM PRIORITY)

Problem: Docstring claimed to handle SDS 1-6 but only SDS 1-2 were implemented, misleading users.

Solution:

• ✅ Enhanced __calculate_sampling_design_state() docstring with:
  • Clear "Currently Implemented" section (SDS 0, 1, 2)
  • Explicit "Not Yet Implemented" section (SDS 3-6)
  • Return value documentation
  • Usage notes and statistical references

Before: Misleading - claimed SDS 1-6 support
After: Accurate - clearly states SDS 0-2 only, with roadmap for 3-6

Benefits:

• Users understand current capabilities
• Clear feature roadmap
• No false expectations

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Impact Summary

Metrics

• Lines removed: 123 (duplicates, print statements)
• Lines added: 293 (logging, constants, documentation)
• Net change: +170 lines (better structure and docs)
• Files changed: 2 (analysis_dataset.py, objects.py)

Quality Improvements

• ✅ Maintainability: Single source of truth for utilities
• ✅ Professionalism: Proper logging infrastructure
• ✅ Readability: Self-documenting constants
• ✅ Accuracy: Honest documentation
• ✅ Testing: All 27 tests passing ✓

Testing

pytest tests/ -v
# ============================== 27 passed in 0.75s ==============================

All existing tests pass without modification, confirming zero breaking changes.

Checklist

• All tests passing (27/27)
• No breaking changes
• Removed dead/duplicate code
• Added professional logging
• Replaced magic numbers with named constants
• Improved documentation accuracy
• Commit message follows conventions

Related Issues

Closes #12
Closes #14
Closes #16
Closes #18

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