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The quantile() function returns records from an input table with _values that fall within a specified quantile or it returns the record with the _value that represents the specified quantile. Which it returns depends on the method used. quantile() supports columns with float values.
*Function type: Aggregate or Selector
**Output data type:* Float | Record
quantile(column: "_value",q: 0.99,method: "estimate_tdigest",compression: 1000.0)
When using the estimate_tdigest or exact_mean methods, it 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
column
The column to use to compute the quantile. Defaults to "_value".
*Data type: String*
q
A value between 0 and 1 indicating the desired quantile.
*Data type: Float*
method
Defines the method of computation.
*Data type: String*
The available options are:
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.
*Data type: Float*
Examples
Quantile as an aggregate
from(bucket: "example-bucket")|> range(start: -5m)|> filter(fn: (r) =>r._measurement == "cpu" andr._field == "usage_system")|> quantile(q: 0.99,method: "estimate_tdigest",compression: 1000.0)
Quantile as a selector
from(bucket: "example-bucket")|> range(start: -5m)|> filter(fn: (r) =>r._measurement == "cpu" andr._field == "usage_system")|> quantile(q: 0.99,method: "exact_selector")
