Why Backtest Data Can Repeat Dates Across Multiple Stocks

Summary

A BigQuant user asks why data in an M4 workflow contains many repeated dates after missing-data handling, with different values on rows sharing a date. The reported test window is May 1 through July 1, while the displayed data begins earlier and has repeated dates across many rows.

The response suggests that each repeated date may correspond to a different stock being tested, with that stock's factor values recorded for the date. This frames the repeats as a likely panel-data structure rather than necessarily a duplication error. The explanation is tentative: the post contains no example rows, verification steps, or resolution, and the follow-up question about joining locally computed factors is left unanswered.

Key ideas

• Repeated dates may represent separate stocks in the backtest universe.
• Different factor values can appear for each stock on the same date.
• The proposed explanation is tentative and is not supported by a worked example.
• The question about adding locally computed factors remains unanswered.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.