difference() function

`difference()` returns the difference between subsequent values.

Subtraction rules for numeric types

• The difference between two non-null values is their algebraic difference; or `null`, if the result is negative and `nonNegative: true`;
• `null` minus some value is always `null`;
• Some value `v` minus `null` is `v` minus the last non-null value seen before `v`; or `null` if `v` is the first non-null value seen.
• If `nonNegative` and `initialZero` are set to `true`, `difference()` returns the difference between `0` and the subsequent value. If the subsequent value is less than zero, `difference()` returns `null`.

Output tables

For each input table with `n` rows, `difference()` outputs a table with `n - 1` rows.

Function type signature
``````(
<-tables: stream[A],
?columns: [string],
?initialZero: bool,
?keepFirst: bool,
?nonNegative: bool,
) => stream[B] where A: Record, B: Record
``````

Parameters

nonNegative

Disallow negative differences. Default is `false`.

When `true`, if a value is less than the previous value, the function assumes the previous value should have been a zero.

columns

List of columns to operate on. Default is `["_value"]`.

keepFirst

Keep the first row in each input table. Default is `false`.

If `true`, the difference of the first row of each output table is null.

initialZero

Use zero (0) as the initial value in the difference calculation when the subsequent value is less than the previous value and `nonNegative` is `true`. Default is `false`.

tables

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

Examples

Calculate the difference between subsequent values

``````import "sampledata"

sampledata.int()
|> difference()
``````

View example input and output

Calculate the non-negative difference between subsequent values

``````import "sampledata"

sampledata.int()
|> difference(nonNegative: true)
``````

View example input and output

Calculate the difference between subsequent values with null values

``````import "sampledata"

sampledata.int(includeNull: true)
|> difference()
``````

View example input and output

Keep the first value when calculating the difference between values

``````import "sampledata"

sampledata.int()
|> difference(keepFirst: true)
``````

View example input and output

Introducing InfluxDB Clustered

A highly available InfluxDB 3.0 cluster on your own infrastructure.

InfluxDB Clustered is a highly available InfluxDB 3.0 cluster built for high write and query workloads on your own infrastructure.

InfluxDB Clustered is currently in limited availability and is only available to a limited group of InfluxData customers. If interested in being part of the limited access group, please contact the InfluxData Sales team.

The future of Flux

Flux is going into maintenance mode. You can continue using it as you currently are without any changes to your code.

Flux is going into maintenance mode and will not be supported in InfluxDB 3.0. This was a decision based on the broad demand for SQL and the continued growth and adoption of InfluxQL. We are continuing to support Flux for users in 1.x and 2.x so you can continue using it with no changes to your code. If you are interested in transitioning to InfluxDB 3.0 and want to future-proof your code, we suggest using InfluxQL.

For information about the future of Flux, see the following:

State of the InfluxDB Cloud Serverless documentation

InfluxDB Cloud Serverless documentation is a work in progress.

The new documentation for InfluxDB Cloud Serverless is a work in progress. We are adding new information and content almost daily. Thank you for your patience!

If there is specific information you’re looking for, please submit a documentation issue.