merge_tdigest()
Applies to: ✅ Azure Data Explorer ✅ Azure Monitor ✅ Microsoft Sentinel
Merges tdigest results (scalar version of the aggregate version tdigest_merge()).
Read more about the underlying algorithm (T-Digest) and the estimated error here.
The
merge_tdigest()andtdigest_merge()functions are equivalent
Important
The results of tdigest() and tdigest_merge() can be stored and later retrieved. For example, you may want to create daily percentiles summary, which can then be used to calculate weekly percentiles. However, the precise binary representation of these results may change over time. There's no guarantee that these functions will produce identical results for identical inputs, and therefore we don't advise relying on them.
Syntax
merge_tdigest(exprs)
Learn more about syntax conventions.
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| exprs | dynamic |
✔️ | One or more comma-separated column references that have the tdigest values to be merged. |
Returns
The result for merging the columns *Expr1*, *Expr2*, ... *ExprN* to one tdigest.
Example
range x from 1 to 10 step 1
| extend y = x + 10
| summarize tdigestX = tdigest(x), tdigestY = tdigest(y)
| project merged = merge_tdigest(tdigestX, tdigestY)
| project percentile_tdigest(merged, 100, typeof(long))
Output
| percentile_tdigest_merged |
|---|
| 20 |