DOCUMENTATION UPDATE COMPLETE - Issue #10 (Benchmark Data Feature)
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SUMMARY OF CHANGES:
Updated CHANGELOG.md with comprehensive benchmark data feature documentation
All changes follow Keep a Changelog format
All file references verified and accurate
All line counts verified against actual source files

FILES MODIFIED:
1. CHANGELOG.md
   Location: Lines 92-115 in Unreleased/Added section
   Added 25 lines documenting the benchmark feature
   Total lines in file: 287 to 312 lines (+25)
   Status: Modified (git tracked)

DOCUMENTATION ADDED:
Feature: Benchmark data retrieval and analysis (Issue #10)

Main Components Documented:
1. get_benchmark_data() - OHLCV data fetching (lines 67-115)
2. get_spy_data() - S&P 500 wrapper (lines 117-136)
3. get_sector_etf_data() - Sector ETF data (lines 138-186)
4. calculate_relative_strength() - IBD-style RS calculation (lines 188-285)
5. calculate_rolling_correlation() - Correlation analysis (lines 287-349)
6. calculate_beta() - Risk measurement (lines 351-441)

Additional Details:
11 sector ETF mappings documented
Error handling and validation documented
Test coverage: 35 total tests (28 unit + 7 integration)
All cross-references include markdown links with line numbers

VERIFICATION RESULTS:
File existence verified (benchmark.py, test_benchmark.py, test_benchmark_integration.py)
Line counts verified (441, 753, 593 lines respectively)
Test function counts verified (28 unit tests, 7 integration tests)
Line number references verified against actual code
Markdown formatting verified for consistency
Entry ordering verified (Issue #10 between #8 and #9)
Keep a Changelog format compliance verified

INLINE DOCUMENTATION STATUS:
Module docstring: Present and comprehensive
Section headers: Present in benchmark.py
Function docstrings: Comprehensive with examples
Inline comments: Section organization headers present
Status: Already documented in source code

STATUS: All documentation updates complete and verified.