convert

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>()

Last modified: 09 December 2024