rename

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

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

nameExpression = (DataColumn) -> String

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

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

20 May 2025