Calculated field
RUNNING_STDEVP(SUM([Revenue]))
Compute using: addressing Period; partitioning Region
Sample data
| Region | Period | Revenue | Cost |
|---|---|---|---|
| Harbor | 1 | 120 | 70 |
| Harbor | 2 | 180 | 100 |
| Harbor | 3 | 180 | 120 |
| Harbor | 4 | 240 | 140 |
| Upland | 1 | 90 | 50 |
| Upland | 2 | 150 | 110 |
| Upland | 3 | null | 90 |
| Upland | 4 | 330 | 190 |
The same calculation as SQL
SELECT CAST((stddev_pop("Revenue") OVER (PARTITION BY "Region" ORDER BY "Period" ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)) AS DOUBLE) AS result FROM input ORDER BY "Region", "Period"Runs the example above.
SELECT CAST((stddev_pop("Revenue") OVER (PARTITION BY "Region" ORDER BY "Period" ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)) AS DOUBLE) AS result FROM input ORDER BY "Region", "Period"Written for this dialect; not run here.
SELECT CAST((stddev_pop(`Revenue`) OVER (PARTITION BY `Region` ORDER BY `Period` ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)) AS FLOAT64) AS result FROM input ORDER BY `Region`, `Period`
Written for this dialect; not run here.
Result
| Region | Period | Revenue | Cost | result |
|---|---|---|---|---|
| Harbor | 1 | 120 | 70 | 0 |
| Harbor | 2 | 180 | 100 | 30 |
| Harbor | 3 | 180 | 120 | 28.2843 |
| Harbor | 4 | 240 | 140 | 42.4264 |
| Upland | 1 | 90 | 50 | 0 |
| Upland | 2 | 150 | 110 | 30 |
| Upland | 3 | null | 90 | 30 |
| Upland | 4 | 330 | 190 | 101.98 |
Same rows from the calculation and from the SQL in DuckDB.
Where a naive translation goes wrong
- Omitting the region partition allows a calculation to consume marks from other regions.
Naive SQL
SELECT CAST((stddev_pop("Revenue") OVER ( ORDER BY "Period" ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)) AS DOUBLE) AS result FROM input ORDER BY "Region", "Period"Region Period Revenue Cost result Harbor 1 120 70 0 Harbor 2 180 100 37.4166 Harbor 3 180 120 34.9857 Harbor 4 240 140 47.9583 Upland 1 90 50 15 Upland 2 150 110 33.541 Upland 3 null 90 34.9857 Upland 4 330 190 74.2307 Matches the calculation
SELECT CAST((stddev_pop("Revenue") OVER (PARTITION BY "Region" ORDER BY "Period" ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)) AS DOUBLE) AS result FROM input ORDER BY "Region", "Period"Region Period Revenue Cost result Harbor 1 120 70 0 Harbor 2 180 100 30 Harbor 3 180 120 28.2843 Harbor 4 240 140 42.4264 Upland 1 90 50 0 Upland 2 150 110 30 Upland 3 null 90 30 Upland 4 330 190 101.98
Signature
RUNNING_STDEVP(expression)