177 lines
5.0 KiB
Markdown
177 lines
5.0 KiB
Markdown
---
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title: Calculate the rate of change
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seotitle: Calculate the rate of change in Flux
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list_title: Rate
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description: >
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Use the `derivative()` function to calculate the rate of change between subsequent values or the
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`aggregate.rate()` function to calculate the average rate of change per window of time.
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If time between points varies, these functions normalize points to a common time interval
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making values easily comparable.
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weight: 10
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menu:
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influxdb_v1:
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parent: Query with Flux
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name: Rate
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list_query_example: rate_of_change
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canonical: /influxdb/v2/query-data/flux/rate/
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alt_links:
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v2: /influxdb/v2/query-data/flux/rate/
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---
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Use the [`derivative()` function](/flux/v0/stdlib/universe/derivative/)
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to calculate the rate of change between subsequent values or the
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[`aggregate.rate()` function](/flux/v0/stdlib/experimental/aggregate/rate/)
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to calculate the average rate of change per window of time.
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If time between points varies, these functions normalize points to a common time interval
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making values easily comparable.
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- [Rate of change between subsequent values](#rate-of-change-between-subsequent-values)
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- [Average rate of change per window of time](#average-rate-of-change-per-window-of-time)
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## Rate of change between subsequent values
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Use the [`derivative()` function](/flux/v0/stdlib/universe/derivative/)
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to calculate the rate of change per unit of time between subsequent _non-null_ values.
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```js
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data
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|> derivative(unit: 1s)
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```
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By default, `derivative()` returns only positive derivative values and replaces negative values with _null_.
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Calculated values are returned as [floats](/flux/v0/language/types/#numeric-types).
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{{< flex >}}
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{{% flex-content %}}
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**Given the following input:**
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| _time | _value |
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|:----- | ------:|
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| 2020-01-01T00:00:00Z | 250 |
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| 2020-01-01T00:04:00Z | 160 |
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| 2020-01-01T00:12:00Z | 150 |
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| 2020-01-01T00:19:00Z | 220 |
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| 2020-01-01T00:32:00Z | 200 |
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| 2020-01-01T00:51:00Z | 290 |
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| 2020-01-01T01:00:00Z | 340 |
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{{% /flex-content %}}
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{{% flex-content %}}
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**`derivative(unit: 1m)` returns:**
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| _time | _value |
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|:----- | ------:|
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| 2020-01-01T00:04:00Z | |
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| 2020-01-01T00:12:00Z | |
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| 2020-01-01T00:19:00Z | 10.0 |
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| 2020-01-01T00:32:00Z | |
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| 2020-01-01T00:51:00Z | 4.74 |
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| 2020-01-01T01:00:00Z | 5.56 |
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{{% /flex-content %}}
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{{< /flex >}}
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Results represent the rate of change **per minute** between subsequent values with
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negative values set to _null_.
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### Return negative derivative values
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To return negative derivative values, set the `nonNegative` parameter to `false`,
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{{< flex >}}
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{{% flex-content %}}
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**Given the following input:**
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| _time | _value |
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|:----- | ------:|
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| 2020-01-01T00:00:00Z | 250 |
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| 2020-01-01T00:04:00Z | 160 |
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| 2020-01-01T00:12:00Z | 150 |
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| 2020-01-01T00:19:00Z | 220 |
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| 2020-01-01T00:32:00Z | 200 |
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| 2020-01-01T00:51:00Z | 290 |
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| 2020-01-01T01:00:00Z | 340 |
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{{% /flex-content %}}
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{{% flex-content %}}
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**The following returns:**
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```js
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|> derivative(
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unit: 1m,
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nonNegative: false
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)
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```
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| _time | _value |
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|:----- | ------:|
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| 2020-01-01T00:04:00Z | -22.5 |
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| 2020-01-01T00:12:00Z | -1.25 |
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| 2020-01-01T00:19:00Z | 10.0 |
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| 2020-01-01T00:32:00Z | -1.54 |
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| 2020-01-01T00:51:00Z | 4.74 |
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| 2020-01-01T01:00:00Z | 5.56 |
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{{% /flex-content %}}
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{{< /flex >}}
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Results represent the rate of change **per minute** between subsequent values and
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include negative values.
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## Average rate of change per window of time
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Use the [`aggregate.rate()` function](/flux/v0/stdlib/experimental/aggregate/rate/)
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to calculate the average rate of change per window of time.
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```js
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import "experimental/aggregate"
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data
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|> aggregate.rate(
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every: 1m,
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unit: 1s,
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groupColumns: ["tag1", "tag2"]
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)
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```
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`aggregate.rate()` returns the average rate of change (as a [float](/flux/v0/language/types/#numeric-types))
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per `unit` for time intervals defined by `every`.
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Negative values are replaced with _null_.
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{{% note %}}
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`aggregate.rate()` does not support `nonNegative: false`.
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{{% /note %}}
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{{< flex >}}
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{{% flex-content %}}
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**Given the following input:**
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| _time | _value |
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|:----- | ------:|
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| 2020-01-01T00:00:00Z | 250 |
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| 2020-01-01T00:04:00Z | 160 |
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| 2020-01-01T00:12:00Z | 150 |
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| 2020-01-01T00:19:00Z | 220 |
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| 2020-01-01T00:32:00Z | 200 |
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| 2020-01-01T00:51:00Z | 290 |
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| 2020-01-01T01:00:00Z | 340 |
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{{% /flex-content %}}
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{{% flex-content %}}
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**The following returns:**
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```js
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|> aggregate.rate(
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every: 20m,
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unit: 1m
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)
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```
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| _time | _value |
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|:----- | ------:|
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| 2020-01-01T00:20:00Z | |
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| 2020-01-01T00:40:00Z | 10.0 |
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| 2020-01-01T01:00:00Z | 4.74 |
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| 2020-01-01T01:20:00Z | 5.56 |
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{{% /flex-content %}}
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{{< /flex >}}
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Results represent the **average change rate per minute** of every **20 minute interval**
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with negative values set to _null_.
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Timestamps represent the right bound of the time window used to average values.
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