---
title: "subscript(_:)"
framework: createml
role: symbol
role_heading: Instance Subscript
path: "createml/mldatatable/subscript(_:)-3opgl"
---

# subscript(_:)

Creates a subset of the table by masking the rows with the given column of Booleans.

## Declaration

```swift
subscript(mask: MLDataColumn<Bool>) -> MLDataTable { get }
```

## Parameters

- `mask`: A Boolean column indicating whether rows should be kept (true) or removed (false) in the derived table.

## Return Value

Return Value A new data table.

## Overview

Overview Use this Boolean column–based subscript to create a new table by masking a subset of the table rows.

For example, to filter the values in a data table as shown above, begin by creating a table with the original data. let data: [String: MLDataValueConvertible] = [     "Title": ["Alice in Wonderland", "Hamlet", "Treasure Island", "Peter Pan"],     "Genre": ["Fantasy", "Drama", "Adventure", "Fantasy"] ]

let table = try? MLDataTable(dictionary: data) else {     fatalError("Invalid dictionary data") } After you create the table, use column arithmetic operators or the map(_:) method to build a row mask. The subscript uses the Boolean values in the row mask to determine whether to keep a row. // Retrieve the "Genre" column from the table. guard let genreColumn = table["Genre", String.self] else {     fatalError("Missing or invalid 'genre' column in table.") }

// Create a new column of Booleans by comparing all of the values // in `Genre` with `Fantasy` using the // `!=(MLDataColumn<String>, String) -> MLDataColumn<Bool>` operator. let noFantasyMask = genreColumn != "Fantasy" Use subscript(mask: MLDataColumn<Bool>) with the Boolean column–row mask to create a filtered table. let noFantasyTable = table[noFantasyMask]