Dataframe
 
0.15
  1. Operations
  2. Modify
  3. Update / convert values
  4. convert

convert

Edit page Last modified: 14 January 2025

Returns DataFrame with changed values in some columns. Allows changing column types.

convert { columnsSelector }
    .with { rowExpression } | .asFrame { frameExpression } | .perRowCol { rowColExpression } | to<Type>() | to { colExpression }

rowExpression = DataRow.(OldValue) -> NewValue
rowColExpression = (DataRow, DataColumn) -> NewValue
colExpression = DataFrame.(DataColumn) -> DataColumn
frameExpression: DataFrame.(DataFrame) -> DataFrame

See column selectors and row expressions

df.convert { age }.with { it.toDouble() }
df.convert { colsAtAnyDepth().colsOf<String>() }.with { it.toCharArray().toList() }

ColumnGroup can be converted using DataFrame API, for example:

df.convert { name }.asFrame { it.add("fullName") { "$firstName $lastName" } }

convert supports automatic type conversions between the following types:

  • String (uses parse to convert from String to other types)

  • Boolean

  • Byte

  • Short

  • Int (and Char)

  • Long

  • Float

  • Double

  • BigDecimal

  • BigInteger

  • LocalDateTime (kotlinx.datetime and java.time)

  • LocalDate (kotlinx.datetime and java.time)

  • LocalTime (kotlinx.datetime and java.time)

  • Instant (kotlinx.datetime and java.time)

df.convert { age }.to<Double>()
df.convert { colsOf<Number>() }.to<String>()
df.convert { name.firstName and name.lastName }.to { it.length() }
df.convert { weight }.toFloat()

Automatic conversion from String to enum classes is also supported:

enum class Direction { NORTH, SOUTH, WEST, EAST }
dataFrameOf("direction")("NORTH", "WEST")
    .convert("direction").to<Direction>()

And finally, Value classes can be used with convert too. Both as conversion source and target:

@JvmInline
value class IntClass(val value: Int)
dataFrameOf("value")("1", "2") // note that values are strings; conversion is done automatically
    .convert("value").to<IntClass>()