---
title: monitor.stateChanges() function
description: >
  `monitor.stateChanges()` detects state changes in a stream of data with a `_level` column
  and outputs records that change from `fromLevel` to `toLevel`.
menu:
  flux_v0_ref:
    name: monitor.stateChanges
    parent: influxdata/influxdb/monitor
    identifier: influxdata/influxdb/monitor/stateChanges
weight: 301
flux/v0/tags: [transformations]
introduced: 0.42.0
---

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`monitor.stateChanges()` detects state changes in a stream of data with a `_level` column
and outputs records that change from `fromLevel` to `toLevel`.



##### Function type signature

```js
(<-tables: stream[{C with _level: D}], ?fromLevel: A, ?toLevel: B) => stream[E] where A: Equatable, B: Equatable, D: Equatable, E: Record
```

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For more information, see [Function type signatures](/flux/v0/function-type-signatures/).
{{% /caption %}}

## Parameters

### fromLevel

Level to detect a change from. Default is `"any"`.



### toLevel

Level to detect a change to. Default is `"any"`.



### tables

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




## Examples

### Detect when the state changes to critical

```js
import "array"
import "influxdata/influxdb/monitor"

data =
    array.from(
        rows: [
            {_time: 2021-01-01T00:00:00Z, _level: "ok"},
            {_time: 2021-01-01T00:01:00Z, _level: "ok"},
            {_time: 2021-01-01T00:02:00Z, _level: "warn"},
            {_time: 2021-01-01T00:03:00Z, _level: "crit"},
        ],
    )

data
    |> monitor.stateChanges(toLevel: "crit")

```

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#### Input data

| _time                | _level  |
| -------------------- | ------- |
| 2021-01-01T00:00:00Z | ok      |
| 2021-01-01T00:01:00Z | ok      |
| 2021-01-01T00:02:00Z | warn    |
| 2021-01-01T00:03:00Z | crit    |


#### Output data

| _time                | *_level |
| -------------------- | ------- |
| 2021-01-01T00:03:00Z | crit    |

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