rank_tdigest()
Applies to: ✅ Azure Data Explorer ✅ Azure Monitor ✅ Microsoft Sentinel
Calculates the approximate rank of the value in a set.
Rank of value v in a set S is defined as count of members of S that are smaller or equal to v, S is represented by its tdigest.
Syntax
rank_tdigest(digest, value)
Learn more about syntax conventions.
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| digest | string |
An expression that was generated by tdigest() or tdigest_merge(). | |
| value | scalar | An expression representing a value to be used for ranking calculation. |
Returns
The rank foreach value in a dataset.
Tip
The values that you want to get its rank must be of the same type as the tdigest.
Examples
In a sorted list (1-1000), the rank of 685 is its index:
range x from 1 to 1000 step 1
| summarize t_x=tdigest(x)
| project rank_of_685=rank_tdigest(t_x, 685)
Output
rank_of_685 |
|---|
685 |
This query calculates the rank of value 4490$ over all damage properties costs:
StormEvents
| summarize tdigestRes = tdigest(DamageProperty)
| project rank_of_4490=rank_tdigest(tdigestRes, 4490)
Output
rank_of_4490 |
|---|
50207 |
Getting the estimated percentage of the rank (by dividing by the set size):
StormEvents
| summarize tdigestRes = tdigest(DamageProperty), count()
| project rank_tdigest(tdigestRes, 4490) * 100.0 / count_
Output
Column1 |
|---|
85.0015237192293 |
The percentile 85 of the damage properties costs is 4490$:
StormEvents
| summarize tdigestRes = tdigest(DamageProperty)
| project percentile_tdigest(tdigestRes, 85, typeof(long))
Output
percentile_tdigest_tdigestRes |
|---|
4490 |