Calculate the rate of change

Use the derivative() function to calculate the rate of change between subsequent values or the aggregate.rate() function to calculate the average rate of change per window of time. If time between points varies, these functions normalize points to a common time interval making values easily comparable.

• Rate of change between subsequent values
• Average rate of change per window of time

Rate of change between subsequent values

Use the derivative() function to calculate the rate of change per unit of time between subsequent non-null values.

data
  |> derivative(unit: 1s)

By default, derivative() returns only positive derivative values and replaces negative values with null. Cacluated values are returned as floats.

Given the following input:

derivative(unit: 1m) returns:

Results represent the rate of change per minute between subsequent values with negative values set to null.

Return negative derivative values

To return negative derivative values, set the nonNegative parameter to false,

Given the following input:

The following returns:

|> derivative(
  unit: 1m,
  nonNegative: false
)

Results represent the rate of change per minute between subsequent values and include negative values.

Average rate of change per window of time

Use the aggregate.rate() function to calculate the average rate of change per window of time.

import "experimental/aggregate"
data
  |> aggregate.rate(
    every: 1m,
    unit: 1s,
    groupColumns: ["tag1", "tag2"]
  )

aggregate.rate() returns the average rate of change (as a float) per unit for time intervals defined by every. Negative values are replaced with null.

aggregate.rate() does not support nonNegative: false.

Given the following input:

The following returns:

|> aggregate.rate(
  every: 20m,
  unit: 1m
)

Results represent the average change rate per minute of every 20 minute interval with negative values set to null. Timestamps represent the right bound of the time window used to average values.