findColumn() function

findColumn() returns an array of values in a specified column from the first table in a stream of tables that matches the specified predicate function.

The function returns an empty array if no table is found or if the column label is not present in the set of columns.

Function type signature

(<-tables: stream[B], column: string, fn: (key: A) => bool) => [C] where A: Record, B: Record

Parameters

column

(Required) Column to extract.

fn

(Required) Predicate function to evaluate input table group keys.

findColumn() uses the first table that resolves as true. The predicate function requires a key argument that represents each input table’s group key as a record.

tables

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

Examples

Extract a column as an array

import "sampledata"

sampledata.int()
    |> findColumn(fn: (key) => key.tag == "t1", column: "_value")// Returns [-2, 10, 7, 17, 15, 4]