experimental.quantile() function

The experimental.quantile() function outputs non-null records with values in the _value column that fall within the specified quantile or represent the specified quantile. Which it returns depends on the method used. The _value column must contain float values.

experimental.quantile() behaves like an aggregate function or a selector function depending on the method used.

import "experimental"

experimental.quantile(
    q: 0.99,
    method: "estimate_tdigest",
    compression: 1000.0,
)

When using the estimate_tdigest or exact_mean methods, the function outputs non-null records with values that fall within the specified quantile.

When using the exact_selector method, it outputs the non-null record with the value that represents the specified quantile.

Parameters

q

A value between 0 and 1 thats specifies the quantile.

method

Computation method. Default is estimate_tdigest.

Available options:

• estimate_tdigest
• exact_mean
• exact_selector

estimate_tdigest

An aggregate method that uses a t-digest data structure to compute an accurate quantile estimate on large data sources.

exact_mean

An aggregate method that takes the average of the two points closest to the quantile value.

exact_selector

A selector method that returns the data point for which at least q points are less than.

compression

Indicates how many centroids to use when compressing the dataset. A larger number produces a more accurate result at the cost of increased memory requirements. Defaults to 1000.0.

tables

Input data. Default is piped-forward data (<-).

Examples

Quantile as an aggregate

import "experimental"

from(bucket: "example-bucket")
    |> range(start: -5m)
    |> filter(fn: (r) => r._measurement == "example-measurement" and r._field == "example-field")
    |> experimental.quantile(q: 0.99, method: "estimate_tdigest", compression: 1000.0)

Quantile as a selector

import "experimental"

from(bucket: "example-bucket")
    |> range(start: -5m)
    |> filter(fn: (r) => r._measurement == "example-measurement" and r._field == "example-field")
    |> experimental.quantile(q: 0.99, method: "exact_selector")