Define what counts as a drawdown
Start with positive, cash-flow-adjusted equity E0. At each observation t, set Pt = max(E0, E1, ..., Et) and underwater depth ut = 1 - Et/Pt. An episode begins when equity falls below its running peak and ends when equity reaches or exceeds that peak. Its depth Dj is the largest ut within that episode. A positive return that leaves equity below the peak does not start a new episode.
- Use all episodes in the chosen window for this calculation. Selecting only the largest k episodes is a different specification; report k if that is the method you need to reproduce.
- Include the deepest observed loss of an unfinished final episode and mark it unrecovered. Its eventual depth and recovery date remain unknown.
- State whether a peak before the test window carries forward. Here E0 is the starting peak; there is no earlier history.
- Consecutive negative-return runs are another possible segmentation. The inspected PerformanceAnalytics BurkeRatio source uses that approach, while its findDrawdowns function tracks underwater episodes. The calculation below follows the stated episode rule, not a claim of identical output from every function named BurkeRatio.