216 lines
5.5 KiB
Markdown
216 lines
5.5 KiB
Markdown
---
|
|
title: histogram() function
|
|
description: >
|
|
`histogram()` approximates the cumulative distribution of a dataset by counting
|
|
data frequencies for a list of bins.
|
|
menu:
|
|
flux_v0_ref:
|
|
name: histogram
|
|
parent: universe
|
|
identifier: universe/histogram
|
|
weight: 101
|
|
flux/v0/tags: [transformations]
|
|
introduced: 0.7.0
|
|
---
|
|
|
|
<!------------------------------------------------------------------------------
|
|
|
|
IMPORTANT: This page was generated from comments in the Flux source code. Any
|
|
edits made directly to this page will be overwritten the next time the
|
|
documentation is generated.
|
|
|
|
To make updates to this documentation, update the function comments above the
|
|
function definition in the Flux source code:
|
|
|
|
https://github.com/influxdata/flux/blob/master/stdlib/universe/universe.flux#L812-L822
|
|
|
|
Contributing to Flux: https://github.com/influxdata/flux#contributing
|
|
Fluxdoc syntax: https://github.com/influxdata/flux/blob/master/docs/fluxdoc.md
|
|
|
|
------------------------------------------------------------------------------->
|
|
|
|
`histogram()` approximates the cumulative distribution of a dataset by counting
|
|
data frequencies for a list of bins.
|
|
|
|
A bin is defined by an upper bound where all data points that are less than
|
|
or equal to the bound are counted in the bin. Bin counts are cumulative.
|
|
|
|
Each input table is converted into a single output table representing a single histogram.
|
|
Each output table has the same group key as the corresponding input table.
|
|
Columns not part of the group key are dropped.
|
|
Output tables include additional columns for the upper bound and count of bins.
|
|
|
|
##### Function type signature
|
|
|
|
```js
|
|
(
|
|
<-tables: stream[A],
|
|
bins: [float],
|
|
?column: string,
|
|
?countColumn: string,
|
|
?normalize: bool,
|
|
?upperBoundColumn: string,
|
|
) => stream[B] where A: Record, B: Record
|
|
```
|
|
|
|
{{% caption %}}
|
|
For more information, see [Function type signatures](/flux/v0/function-type-signatures/).
|
|
{{% /caption %}}
|
|
|
|
## Parameters
|
|
|
|
### column
|
|
|
|
Column containing input values. Column must be of type float.
|
|
Default is `_value`.
|
|
|
|
|
|
|
|
### upperBoundColumn
|
|
|
|
Column to store bin upper bounds in. Default is `le`.
|
|
|
|
|
|
|
|
### countColumn
|
|
|
|
Column to store bin counts in. Default is `_value`.
|
|
|
|
|
|
|
|
### bins
|
|
({{< req >}})
|
|
List of upper bounds to use when computing the histogram frequencies.
|
|
|
|
Bins should contain a bin whose bound is the maximum value of the data set.
|
|
This value can be set to positive infinity if no maximum is known.
|
|
#### Bin helper functions
|
|
The following helper functions can be used to generated bins.
|
|
- linearBins()
|
|
- logarithmicBins()
|
|
|
|
### normalize
|
|
|
|
Convert counts into frequency values between 0 and 1.
|
|
Default is `false`.
|
|
|
|
**Note**: Normalized histograms cannot be aggregated by summing their counts.
|
|
|
|
### tables
|
|
|
|
Input data. Default is piped-forward data (`<-`).
|
|
|
|
|
|
|
|
|
|
## Examples
|
|
|
|
- [Create a cumulative histogram](#create-a-cumulative-histogram)
|
|
- [Create a cumulative histogram with dynamically generated bins](#create-a-cumulative-histogram-with-dynamically-generated-bins)
|
|
|
|
### Create a cumulative histogram
|
|
|
|
```js
|
|
import "sampledata"
|
|
|
|
sampledata.float()
|
|
|> histogram(bins: [0.0, 5.0, 10.0, 20.0])
|
|
|
|
```
|
|
|
|
{{< expand-wrapper >}}
|
|
{{% expand "View example input and output" %}}
|
|
|
|
#### Input data
|
|
|
|
| _time | *tag | _value |
|
|
| -------------------- | ---- | ------- |
|
|
| 2021-01-01T00:00:00Z | t1 | -2.18 |
|
|
| 2021-01-01T00:00:10Z | t1 | 10.92 |
|
|
| 2021-01-01T00:00:20Z | t1 | 7.35 |
|
|
| 2021-01-01T00:00:30Z | t1 | 17.53 |
|
|
| 2021-01-01T00:00:40Z | t1 | 15.23 |
|
|
| 2021-01-01T00:00:50Z | t1 | 4.43 |
|
|
|
|
| _time | *tag | _value |
|
|
| -------------------- | ---- | ------- |
|
|
| 2021-01-01T00:00:00Z | t2 | 19.85 |
|
|
| 2021-01-01T00:00:10Z | t2 | 4.97 |
|
|
| 2021-01-01T00:00:20Z | t2 | -3.75 |
|
|
| 2021-01-01T00:00:30Z | t2 | 19.77 |
|
|
| 2021-01-01T00:00:40Z | t2 | 13.86 |
|
|
| 2021-01-01T00:00:50Z | t2 | 1.86 |
|
|
|
|
|
|
#### Output data
|
|
|
|
| *tag | le | _value |
|
|
| ---- | --- | ------- |
|
|
| t1 | 0 | 1 |
|
|
| t1 | 5 | 2 |
|
|
| t1 | 10 | 3 |
|
|
| t1 | 20 | 6 |
|
|
|
|
| *tag | le | _value |
|
|
| ---- | --- | ------- |
|
|
| t2 | 0 | 1 |
|
|
| t2 | 5 | 3 |
|
|
| t2 | 10 | 3 |
|
|
| t2 | 20 | 6 |
|
|
|
|
{{% /expand %}}
|
|
{{< /expand-wrapper >}}
|
|
|
|
### Create a cumulative histogram with dynamically generated bins
|
|
|
|
```js
|
|
import "sampledata"
|
|
|
|
sampledata.float()
|
|
|> histogram(bins: linearBins(start: 0.0, width: 4.0, count: 3))
|
|
|
|
```
|
|
|
|
{{< expand-wrapper >}}
|
|
{{% expand "View example input and output" %}}
|
|
|
|
#### Input data
|
|
|
|
| _time | *tag | _value |
|
|
| -------------------- | ---- | ------- |
|
|
| 2021-01-01T00:00:00Z | t1 | -2.18 |
|
|
| 2021-01-01T00:00:10Z | t1 | 10.92 |
|
|
| 2021-01-01T00:00:20Z | t1 | 7.35 |
|
|
| 2021-01-01T00:00:30Z | t1 | 17.53 |
|
|
| 2021-01-01T00:00:40Z | t1 | 15.23 |
|
|
| 2021-01-01T00:00:50Z | t1 | 4.43 |
|
|
|
|
| _time | *tag | _value |
|
|
| -------------------- | ---- | ------- |
|
|
| 2021-01-01T00:00:00Z | t2 | 19.85 |
|
|
| 2021-01-01T00:00:10Z | t2 | 4.97 |
|
|
| 2021-01-01T00:00:20Z | t2 | -3.75 |
|
|
| 2021-01-01T00:00:30Z | t2 | 19.77 |
|
|
| 2021-01-01T00:00:40Z | t2 | 13.86 |
|
|
| 2021-01-01T00:00:50Z | t2 | 1.86 |
|
|
|
|
|
|
#### Output data
|
|
|
|
| *tag | le | _value |
|
|
| ---- | ---- | ------- |
|
|
| t1 | 0 | 1 |
|
|
| t1 | 4 | 1 |
|
|
| t1 | 8 | 3 |
|
|
| t1 | +Inf | 6 |
|
|
|
|
| *tag | le | _value |
|
|
| ---- | ---- | ------- |
|
|
| t2 | 0 | 1 |
|
|
| t2 | 4 | 2 |
|
|
| t2 | 8 | 3 |
|
|
| t2 | +Inf | 6 |
|
|
|
|
{{% /expand %}}
|
|
{{< /expand-wrapper >}}
|