tdigest() (aggregation function)

Calculates the intermediate results of percentiles() across the group.

Note

This function is used in conjunction with the summarize operator.

For more information, see the underlying algorithm (T-Digest) and the estimated error.

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

tdigest(expr [, weight])

Learn more about syntax conventions.

Parameters

Name Type Required Description
expr string ✔️ The expression used for the aggregation calculation.
weight string The weights of the values for the aggregation calculation.

Returns

The Intermediate results of weighted percentiles of *expr* across the group.

Tip

  • Use the aggregation function tdigest_merge() to merge the output of tdigest again across another group.
  • Use the function percentile_tdigest() to calculate the percentile/percentilew of the tdigest results.

Examples

This example shows the results of the tdigest percentiles sorted by state.

StormEvents
| summarize tdigest(DamageProperty) by State

The results table shown includes only the first 10 rows.

State tdigest_DamageProperty
NEBRASKA [[7],[800,250,300000,5000,240000,1500000,20000,550000,0,75000,100000,1000,10000,30000,13000,2000000,1000000,650000,125000,35000,7000,2500000,4000000,450000,85000,460000,500000,6000,150000,350000,4000,72500,1200000,180000,400000,25000,50000,2000,45000,8000,120000,200000,40000,1200,15000,55000,3000,250000],[5,1,3,72,1,1,44,1,1351,12,24,17,46,13,6,1,2,1,2,6,8,1,1,1,2,1,4,2,6,1,2,2,1,1,2,26,18,12,2,2,1,7,6,4,28,4,6,6]]
MINNESOTA [[7],[700,500,2000000,2500,1200000,12000000,16000,7000000,0,300000,425000,750,6000,30000,10000,22000000,10000000,9600000,600000,50000,4000,27000000,35000000,4000000,400000,5000000,6000000,3000,750000,2500000,2000,250000,11000000,38000000,3000000,20000,120000,1000,100000,5000,500000,1000000,60000,800,15000,200000,1500,1500000,900000],[1,3,1,3,1,2,1,1,1793,1,1,2,2,2,3,1,1,1,2,2,1,1,1,1,2,1,2,1,1,1,6,1,1,1,3,5,1,5,2,5,2,2,1,2,2,2,2,1,1]]
KANSAS [[7],[667,200,6000000,3400,80000,300000,18875,210000,0,45857,750000,37500000,10000,81150000,15000000,6400000,2570000,225000,59400,25000,5000,400000,7000000,4500000,2500000,6500000,200000,4500,70000,122500,2785,12000000,1900000,18200000,150000,1150000,27000000,2000,30000,2000000,250000000,75000,26000,1500,1500000,1000000,2500,100000,21600000,50000,335000,600000,175000,500000,160000,51000,40000,20000,15000,252500,7520,350000,250000,3400000,1000,338000,16000000,106000,4840000,305000,540000,337500,9800000,45000,12500,700000,4000000,71000,30000000,35000,3700000,22000,56000],[12,2,2,5,2,3,8,1,2751,7,2,1,37,1,1,1,1,2,5,12,33,8,1,1,1,2,10,1,5,2,7,1,4,1,5,1,1,9,11,4,1,5,2,6,4,8,2,23,1,44,2,3,2,3,1,1,1,18,5,2,5,1,7,1,25,1,1,3,1,1,1,2,6,1,1,2,1,1,1,3,1,1,1]]
NEW MEXICO [[7],[600,500,2500000,7000,1500,28000,40000,10000,0,500000,20000,1000,21000,70000,25000,3500000,200000,16500000,50000,100000,15000,4000,5000,2000],[1,3,1,1,1,1,1,7,466,1,7,4,1,1,2,1,1,1,1,2,1,4,10,8]]
KENTUCKY [[7],[600,200,700000,5000,400000,12000,15000,100000,0,60000,80000,1000,9000,20000,10000,50000,30000,300000,120000,25000,7000,3000,500000,11500000,75000,35000,8000,6000,150000,1500000,4000,56000,1911,250000,2500000,18000,45000,2000],[6,2,1,42,1,3,9,8,999,2,1,52,1,21,37,25,7,2,3,14,11,35,1,1,6,10,9,10,4,1,13,1,9,3,1,2,1,37]]
VIRGINIA [[7],[536,500,125000,3000,100000,7250,8000,60000,0,40000,50000,956,6000,11500,7000,25000,15000,98000,70000,12000,4000,2000,120000,1000000,45000,16000,5000,3500,75000,175000,2500,30000,1000,80000,300000,10000,20000,1500],[7,11,1,48,2,2,2,1,1025,2,6,9,2,2,1,5,16,1,3,5,12,122,1,1,1,1,64,2,2,1,1,7,209,3,2,42,19,6]]
OREGON [[7],[5000,1000,60000,434000,20000,50000,100000,500000,0,1500000,20400000,6000,62600000],[8,2,1,1,1,1,3,1,401,1,1,1,1]]
ALASKA [[7],[5000,1000,25000,700000,12060,15000,100000,1600000,0,10000],[5,1,1,1,1,2,1,2,242,1]]
CONNECTICUT [[7],[5000,1000,2000000,0,50000,750000,6000],[1,1,1,142,1,1,1]]
NEVADA [[7],[5000,1000,200000,1000000,30000,40000,297000,5000000,0,10000],[4,2,1,1,1,1,1,1,148,3]]