findColumn() function

The findColumn() function returns an array of values in a specified column from the first table in a stream of tables where the group key values match the specified predicate. The function returns an empty array if no table is found or if the column label is not present in the set of columns.

*Function type: Stream and table*

findColumn(
  fn: (key) => key._field == "fieldName")
  column: "_value"
)

Parameters

fn

A predicate function for matching keys in a table’s group key. Expects a key argument that represents a group key in the input stream.

*Data type: Function*

column

Name of the column to extract.

*Data type: String*

Example

vs = from(bucket:"example-bucket")
    |> range(start: -5m)
    |> filter(fn:(r) => r._measurement == "cpu")
    |> findColumn(
      fn: (key) => key._field == "usage_idle",
      column: "_value"
    )
// Use column values
x = vs[0] + vs[1]

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