84 lines
2.1 KiB
Markdown
84 lines
2.1 KiB
Markdown
---
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title: findColumn() function
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description: >
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`findColumn()` returns an array of values in a specified column from the first
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table in a stream of tables that matches the specified predicate function.
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menu:
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flux_v0_ref:
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name: findColumn
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parent: universe
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identifier: universe/findColumn
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weight: 101
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flux/v0/tags: [dynamic queries]
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introduced: 0.68.0
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---
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<!------------------------------------------------------------------------------
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IMPORTANT: This page was generated from comments in the Flux source code. Any
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edits made directly to this page will be overwritten the next time the
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documentation is generated.
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To make updates to this documentation, update the function comments above the
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function definition in the Flux source code:
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https://github.com/influxdata/flux/blob/master/stdlib/universe/universe.flux#L3057-L3060
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Contributing to Flux: https://github.com/influxdata/flux#contributing
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Fluxdoc syntax: https://github.com/influxdata/flux/blob/master/docs/fluxdoc.md
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------------------------------------------------------------------------------->
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`findColumn()` returns an array of values in a specified column from the first
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table in a stream of tables that matches the specified predicate function.
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The function returns an empty array if no table is found or if the column
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label is not present in the set of columns.
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##### Function type signature
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```js
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(<-tables: stream[B], column: string, fn: (key: A) => bool) => [C] where A: Record, B: Record
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```
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{{% caption %}}
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For more information, see [Function type signatures](/flux/v0/function-type-signatures/).
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{{% /caption %}}
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## Parameters
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### column
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({{< req >}})
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Column to extract.
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### fn
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({{< req >}})
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Predicate function to evaluate input table group keys.
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`findColumn()` uses the first table that resolves as `true`.
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The predicate function requires a `key` argument that represents each input
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table's group key as a record.
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### tables
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Input data. Default is piped-forward data (`<-`).
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## Examples
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### Extract a column as an array
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```js
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import "sampledata"
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sampledata.int()
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|> findColumn(fn: (key) => key.tag == "t1", column: "_value")// Returns [-2, 10, 7, 17, 15, 4]
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```
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