DataColumn

Edit pageLast modified: 24 October 2025

DataColumn represents a column of values. It can store objects of primitive or reference types, or other DataFrame objects.

See how to create columns

Properties

  • name: String — name of the column; should be unique within containing dataframe

  • path: ColumnPath — path to the column; depends on the way column was retrieved from dataframe

  • type: KType — type of elements in the column

  • hasNulls: Boolean — flag indicating whether column contains null values

  • values: Iterable<T> — column data

  • size: Int — number of elements in the column

Column kinds

DataColumn instances can be one of three subtypes: ValueColumn, ColumnGroup or FrameColumn

ValueColumn

Represents a sequence of values.

It can store values of primitive (integers, strings, decimals, etc.) or reference types. Currently, it uses List as underlying data storage.

ColumnGroup

Container for nested columns. Used to create column hierarchy.

You can create column groups using the group operation or by splitting inward — see group and split for details.

FrameColumn

Special case of ValueColumn that stores another DataFrame objects as elements.

DataFrame stored in FrameColumn may have different schemas.

FrameColumn may appear after reading from JSON or other hierarchical data structures, or after grouping operations such as groupBy or pivot.