Calculate Cumulative Volume Separately for Each Stock
Summary
This short discussion explains how to compute a running total of traded amount separately for each stock in a multi-instrument dataset. A single cumulative sum across the full table combines all instruments, so the suggested approach groups rows by instrument and applies the cumulative calculation within each group.
Within each group, rows are sorted by date before the running total is calculated, ensuring the accumulation follows chronological order. The answer demonstrates the general group-then-apply pattern and names a custom function as the way to implement it. It does not address visualization beyond the original question, provide example output, or discuss data issues such as duplicate dates, missing observations, or whether volume should be reset at a particular period. The method is a basic data-processing technique, not a trading signal or performance claim.
Key ideas
- A cumulative sum over multiple stocks should be partitioned by instrument to avoid mixing their traded amounts.
- Sort each instrument’s observations by date before computing its running total.
- A per-group function can apply the cumulative calculation and return the augmented data.
- The answer does not explain visualization or define reset rules for the accumulation.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.