129 lines
3.8 KiB
Markdown
129 lines
3.8 KiB
Markdown
---
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title: stateCount() function
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description: >
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`stateCount()` returns the number of consecutive rows in a given state.
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menu:
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flux_v0_ref:
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name: stateCount
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parent: universe
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identifier: universe/stateCount
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weight: 101
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flux/v0/tags: [transformations]
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introduced: 0.7.0
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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#L4026-L4028
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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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`stateCount()` returns the number of consecutive rows in a given state.
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The state is defined by the `fn` predicate function. For each consecutive
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record that evaluates to `true`, the state count is incremented. When a record
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evaluates to `false`, the value is set to `-1` and the state count is reset.
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If the record generates an error during evaluation, the point is discarded,
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and does not affect the state count.
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The state count is added as an additional column to each record.
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##### Function type signature
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```js
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(<-tables: stream[A], fn: (r: A) => bool, ?column: string) => stream[B] 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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### fn
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({{< req >}})
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Predicate function that identifies the state of a record.
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### column
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Column to store the state count in. Default is `stateCount`.
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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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### Count the number rows in a specific state
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```js
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import "sampledata"
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sampledata.int()
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|> stateCount(fn: (r) => r._value < 10)
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```
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{{< expand-wrapper >}}
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{{% expand "View example input and output" %}}
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#### Input data
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| _time | _value | *tag |
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| -------------------- | ------- | ---- |
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| 2021-01-01T00:00:00Z | -2 | t1 |
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| 2021-01-01T00:00:10Z | 10 | t1 |
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| 2021-01-01T00:00:20Z | 7 | t1 |
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| 2021-01-01T00:00:30Z | 17 | t1 |
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| 2021-01-01T00:00:40Z | 15 | t1 |
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| 2021-01-01T00:00:50Z | 4 | t1 |
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| _time | _value | *tag |
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| -------------------- | ------- | ---- |
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| 2021-01-01T00:00:00Z | 19 | t2 |
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| 2021-01-01T00:00:10Z | 4 | t2 |
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| 2021-01-01T00:00:20Z | -3 | t2 |
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| 2021-01-01T00:00:30Z | 19 | t2 |
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| 2021-01-01T00:00:40Z | 13 | t2 |
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| 2021-01-01T00:00:50Z | 1 | t2 |
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#### Output data
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| _time | _value | *tag | stateCount |
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| -------------------- | ------- | ---- | ----------- |
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| 2021-01-01T00:00:00Z | -2 | t1 | 1 |
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| 2021-01-01T00:00:10Z | 10 | t1 | -1 |
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| 2021-01-01T00:00:20Z | 7 | t1 | 1 |
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| 2021-01-01T00:00:30Z | 17 | t1 | -1 |
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| 2021-01-01T00:00:40Z | 15 | t1 | -1 |
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| 2021-01-01T00:00:50Z | 4 | t1 | 1 |
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| _time | _value | *tag | stateCount |
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| -------------------- | ------- | ---- | ----------- |
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| 2021-01-01T00:00:00Z | 19 | t2 | -1 |
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| 2021-01-01T00:00:10Z | 4 | t2 | 1 |
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| 2021-01-01T00:00:20Z | -3 | t2 | 2 |
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| 2021-01-01T00:00:30Z | 19 | t2 | -1 |
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| 2021-01-01T00:00:40Z | 13 | t2 | -1 |
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| 2021-01-01T00:00:50Z | 1 | t2 | 1 |
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{{% /expand %}}
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{{< /expand-wrapper >}}
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