subscript(_:)

Retrieves or adds an untyped column with the specified name.

Declaration

subscript(columnName: String) -> MLUntypedColumn { get set }

Parameters

columnName:
The name of the column to extract from or add to the datatable.

Return Value

A new MLUntypedColumn with the specified name, if it exists; otherwise an invalid column.

Overview

Use this subscript to retrieve an MLUntypedColumn or add a new one to the data table.

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For example, to extract, convert, and add a column as shown above, begin by creating a data table.

let data: [String: MLDataValueConvertible] = [
    "Planet": ["Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune"],
    "Distance (AU)": [0.39, 0.72, 1.00, 1.52, 5.20, 9.54, 19.22, 30.06]
]

var table = try MLDataTable(dictionary: data)

After creating the table, extract a column.

let distanceInAU = table["Distance (AU)"]

Use the untyped column’s multiplication operator to create a new column of data.

// Create a new column of Doubles by multiplying all the the values in
// `distanceInAU` by 149,597,870.7 (the number of km in an astronomical unit)
let distanceInKm = (distanceInAU * 149_597_870.700)

Finally, use the subscript(_:) to add the new column to a table with a different name.

table["Distance (km)"] = distanceInKm