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findColumn() function

content/flux/v0/stdlib/universe/findcolumn.md

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<!------------------------------------------------------------------------------ IMPORTANT: This page was generated from comments in the Flux source code. Any edits made directly to this page will be overwritten the next time the documentation is generated. To make updates to this documentation, update the function comments above the function definition in the Flux source code: https://github.com/influxdata/flux/blob/master/stdlib/universe/universe.flux#L3057-L3060 Contributing to Flux: https://github.com/influxdata/flux#contributing Fluxdoc syntax: https://github.com/influxdata/flux/blob/master/docs/fluxdoc.md ------------------------------------------------------------------------------->

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

{{% caption %}} For more information, see Function type signatures. {{% /caption %}}

Parameters

column

({{< req >}}) Column to extract.

fn

({{< req >}}) 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

js
import "sampledata"

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