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Renames one or several columns without changing its location in DataFrame.

df.rename { columns }.into(name)
df.rename { columns }.into { nameExpression }

nameExpression = (DataColumn) -> String

Related operations:

See column selectors for how to select the columns for this operation.

df.rename { name }.into("fullName")
df.rename("name").into("fullName")

df.rename { age }.into {
    val mean = it.data.mean()
    "age [mean = $mean]"
}
df.rename("age").into {
    val mean = it.data.cast<Int>().mean()
    "age [mean = $mean]"
}

renameToCamelCase

A special case of rename that renames all column names in a DataFrame to "camelCase" format.

This function standardizes column names by converting them from various naming styles—such as "snake_case", "PascalCase", "kebab-case", or "space delimited formats" into a consistent "camelCase" form.

The transformation follows Kotlin naming conventions for variables and properties, making the resulting column names idiomatic and easier to use in Kotlin code, which is especially useful in extension properties usage.

Use it right after loading raw data to normalize column names into a consistent format. This is especially helpful when preparing the data for further transformations, column access, or integration with Kotlin APIs—making the DataFrame easier and more predictable to work with.

Examples

df

Rename selected columns to "camelCase":

df.rename { ColumnA and `COLUMN-C` }.toCamelCase()

Rename all columns (including nested) to "camelCase":

df.renameToCamelCase()

Transformation Rules and Examples

  • Delimiters (underscores, dashes, spaces, etc.) are removed.
  • The first word is kept lowercase; all subsequent words are capitalized.
  • An underscore is inserted between consecutive numbers to improve readability.
  • If a name contains no letters or digits, it remains unchanged.
Original camelCase
hello_world helloWorld
HelloWorld helloWorld
json.parser.Config jsonParserConfig
my.var_name test myVarNameTest
thirdColumn thirdColumn
someHTMLParser someHtmlParser
RESTApi restApi
OAuth2Token oAuth2Token
GraphQLQuery graphQlQuery
TCP_3_PROTOCOL tcp3Protocol
123hello_world456 123HelloWorld456
API_Response_2023 apiResponse2023
UPPER_case-LOWER upperCaseLower
12parse34CamelCase 12Parse34CamelCase
snake_case_example snakeCaseExample
dot.separated.words dotSeparatedWords
kebab-case-example kebabCaseExample
MIXED_Case_with_123Numbers mixedCaseWith123Numbers
!!! !!!
1000.2000.3000 1000_2000_3000
UPPERCASE uppercase
alreadyCamelCased alreadyCamelCased
justNumbers123 justNumbers123
Just_Special$Chars!! justSpecialChars
singleword singleword
word_with_underscores_and-dashes wordWithUnderscoresAndDashes
10-20-aa 10_20Aa