115 lines
3.8 KiB
Markdown
115 lines
3.8 KiB
Markdown
---
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title: stateDuration() function
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description: The `stateDuration()` function computes the duration of a given state.
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aliases:
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- /influxdb/v2.0/reference/flux/functions/transformations/stateduration
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- /influxdb/v2.0/reference/flux/functions/built-in/transformations/stateduration/
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- /influxdb/v2.0/reference/flux/stdlib/built-in/transformations/stateduration/
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- /influxdb/cloud/reference/flux/stdlib/built-in/transformations/stateduration/
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menu:
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flux_0_x_ref:
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name: stateDuration
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parent: universe
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weight: 102
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flux/v0.x/tags: [transformations]
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related:
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- /{{< latest "influxdb" >}}/query-data/flux/monitor-states/
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- /flux/v0.x/stdlib/contrib/tomhollingworth/events/duration/
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introduced: 0.7.0
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---
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`stateDuration()` returns the cumulative duration of 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 duration is incremented by the
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duration of time between records using the specified `unit`. When a record
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evaluates to `false`, the value is set to `-1` and the state duration 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 duration.
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The state duration is added as an additional column to each record.
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The duration is represented as an integer in the units specified.
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{{% note %}}
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As the first point in the given state has no previous point, its
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state duration will be 0.
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{{% /note %}}
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```js
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stateDuration(fn: (r) => r._measurement == "state", column: "stateDuration", unit: 1s)
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```
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_If the expression generates an error during evaluation, the point is discarded,
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and does not affect the state duration._
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## Parameters
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{{% note %}}
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Make sure `fn` parameter names match each specified parameter. To learn why, see [Match parameter names](/flux/v0.x/spec/data-model/#match-parameter-names).
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{{% /note %}}
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### fn {data-type="function"}
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({{< req >}})
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A single argument function that evaluates true or false to identify the state of the record.
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Records are passed to the function.
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Those that evaluate to `true` increment the state duration.
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Those that evaluate to `false` reset the state duration.
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### column {data-type="string"}
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Name of the column added to each record that contains the state duration.
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Default is `stateDuration`.
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### unit {data-type="duration"}
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Unit of time to increment state duration with.
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For example: `1s`, `1m`, `1h`, etc.
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Default is one second (`1s`).
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### tables {data-type="stream of tables"}
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Input data.
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Default is piped-forward data ([`<-`](/flux/v0.x/spec/expressions/#pipe-expressions)).
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## Examples
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{{% flux/sample-example-intro %}}
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```js
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import "sampledata"
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sampledata.int()
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|> stateDuration(fn: (r) => r._value > 10)
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```
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{{< expand-wrapper >}}
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{{% expand "View input and output" %}}
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{{< flex >}}
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{{% flex-content %}}
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##### Input data
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{{% flux/sample "int" %}}
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{{% /flex-content %}}
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{{% flex-content %}}
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##### Output data
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| _time | tag | _value | stateDuration |
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| :------------------- | :-- | -----: | ------------: |
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| 2021-01-01T00:00:00Z | t1 | -2 | -1 |
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| 2021-01-01T00:00:10Z | t1 | 10 | -1 |
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| 2021-01-01T00:00:20Z | t1 | 7 | -1 |
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| 2021-01-01T00:00:30Z | t1 | 17 | 0 |
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| 2021-01-01T00:00:40Z | t1 | 15 | 10 |
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| 2021-01-01T00:00:50Z | t1 | 4 | -1 |
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| _time | tag | _value | stateDuration |
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| :------------------- | :-- | -----: | ------------: |
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| 2021-01-01T00:00:00Z | t2 | 19 | 0 |
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| 2021-01-01T00:00:10Z | t2 | 4 | -1 |
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| 2021-01-01T00:00:20Z | t2 | -3 | -1 |
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| 2021-01-01T00:00:30Z | t2 | 19 | 0 |
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| 2021-01-01T00:00:40Z | t2 | 13 | 10 |
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| 2021-01-01T00:00:50Z | t2 | 1 | -1 |
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{{% /flex-content %}}
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{{< /flex >}}
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{{% /expand %}}
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{{< /expand-wrapper >}}
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