129 lines
3.6 KiB
Markdown
129 lines
3.6 KiB
Markdown
---
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title: relativeStrengthIndex() function
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description: >
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`relativeStrengthIndex()` measures the relative speed and change of values in input tables.
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menu:
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flux_v0_ref:
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name: relativeStrengthIndex
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parent: universe
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identifier: universe/relativeStrengthIndex
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weight: 101
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flux/v0/tags: [transformations]
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introduced: 0.38.0
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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#L2236-L2239
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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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`relativeStrengthIndex()` measures the relative speed and change of values in input tables.
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### Relative strength index (RSI) rules
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- The general equation for calculating a relative strength index (RSI) is
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`RSI = 100 - (100 / (1 + (AVG GAIN / AVG LOSS)))`.
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- For the first value of the RSI, `AVG GAIN` and `AVG LOSS` are averages of the `n` period.
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- For subsequent calculations:
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- `AVG GAIN` = `((PREVIOUS AVG GAIN) * (n - 1)) / n`
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- `AVG LOSS` = `((PREVIOUS AVG LOSS) * (n - 1)) / n`
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- `relativeStrengthIndex()` ignores `null` values.
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### Output tables
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For each input table with `x` rows, `relativeStrengthIndex()` outputs a table
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with `x - n` rows.
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##### Function type signature
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```js
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(<-tables: stream[A], n: int, ?columns: [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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### n
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({{< req >}})
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Number of values to use to calculate the RSI.
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### columns
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Columns to operate on. Default is `["_value"]`.
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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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### Calculate a three point relative strength index
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```js
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import "sampledata"
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sampledata.int()
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|> relativeStrengthIndex(n: 3)
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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 |
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| -------------------- | ------------------ | ---- |
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| 2021-01-01T00:00:30Z | 84.375 | t1 |
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| 2021-01-01T00:00:40Z | 73.97260273972603 | t1 |
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| 2021-01-01T00:00:50Z | 36.672325976230894 | t1 |
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| _time | _value | *tag |
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| -------------------- | ----------------- | ---- |
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| 2021-01-01T00:00:30Z | 70.27027027027026 | t2 |
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| 2021-01-01T00:00:40Z | 59.42857142857142 | t2 |
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| 2021-01-01T00:00:50Z | 40.625 | t2 |
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{{% /expand %}}
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{{< /expand-wrapper >}}
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