Add IRR function for calculating internal rate of return #1598
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Implement the IRR (Internal Rate of Return) function following Excel specification. IRR calculates the internal rate of return for a series of cash flows represented by the numbers in values. Features: - Takes a range of cash flow values and optional guess parameter - Uses Newton-Raphson method for iterative calculation - Returns #NUM! if algorithm does not converge or values lack both positive and negative values - Returns result as NUMBER_PERCENT type - Includes translations for all 17 built-in languages
Performance comparison of head (c4a4933) vs base (7f856be) |
- Add guess <= -1 validation returning #VALUE! (consistent with RATE) - Add Newton's method comment to irr method - Add tests for guess = -1 and guess < -1 edge cases - Add test for empty range - Add test for named ranges
- Add test for minimum valid cash flow (one positive, one negative) - Add test for negative return rate - Add test for IRR close to zero - Add test for IRR of exactly zero - Add test for initial positive followed by negative cash flows - Add test for alternating positive and negative values - Add test for cell reference update propagation
- Remove upfront guess <= -1 check (was returning #VALUE! incorrectly) - Algorithm can find valid IRR even with guess < -1 (e.g., IRR=-200%) - guess = -1 still returns #NUM! (caught by iteration check) - Refactor positive/negative check to use Array.some() for clarity - Update tests to reflect correct behavior
- Add test for derivative too small condition (line 869)
Uses cash flows {-0.5, 2, -1} with guess=0 where dnpv=0 but npv!=0
- Add test for max iterations reached (line 888)
Uses cash flows {-1, 2, -1.0001} with guess=0.9 causing oscillation
Co-authored-by: Krzysztof ‘Budzio’ Budnik <[email protected]>
budnix
approved these changes
Jan 8, 2026
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## develop #1598 +/- ##
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Coverage 97.17% 97.17%
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Files 170 170
Lines 14747 14785 +38
Branches 3236 3245 +9
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+ Hits 14330 14368 +38
Misses 409 409
Partials 8 8
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Implemented with the assist of Claude Code + Claude Opus 4.5
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