Write

df.writeCsv(file)

val csvStr = df.toCsvStr(delimiter = ';', recordSeparator = System.lineSeparator())

df.writeJson(file)

val jsonStr = df.toJson(prettyPrint = true)

implementation("org.jetbrains.kotlinx:dataframe-excel:$dataframe_version")

df.writeExcel(file)

/**
 * Do something with generated sheets. Here we set bold style for headers and italic style for first data column
 */
fun setStyles(sheet: Sheet) {
    val headerFont = sheet.workbook.createFont()
    headerFont.bold = true
    val headerStyle = sheet.workbook.createCellStyle()
    headerStyle.setFont(headerFont)

    val indexFont = sheet.workbook.createFont()
    indexFont.italic = true
    val indexStyle = sheet.workbook.createCellStyle()
    indexStyle.setFont(indexFont)

    sheet.forEachIndexed { index, row ->
        if (index == 0) {
            for (cell in row) {
                cell.cellStyle = headerStyle
            }
        } else {
            row.first().cellStyle = indexStyle
        }
    }
}

// Create a workbook (or use existing)
val wb = WorkbookFactory.create(true)

// Create different sheets from different data frames in the workbook
val allPersonsSheet = df.writeExcel(wb, sheetName = "allPersons")
val happyPersonsSheet =
    df.filter { person -> person.isHappy }.remove("isHappy").writeExcel(wb, sheetName = "happyPersons")
val unhappyPersonsSheet =
    df.filter { person -> !person.isHappy }.remove("isHappy").writeExcel(wb, sheetName = "unhappyPersons")

// Do anything you want by POI
listOf(happyPersonsSheet, unhappyPersonsSheet).forEach { setStyles(it) }

// Save the result
file.outputStream().use { wb.write(it) }
wb.close()

// Create a new Excel workbook with a single sheet called "allPersons", replacing the file if it already exists -> Current sheets: allPersons
df.writeExcel(file, sheetName = "allPersons")
// Add a new sheet to the previous file without replacing it, by setting keepFile = true -> Current sheets: allPersons, happyPersons
df.filter { person -> person.isHappy }.remove("isHappy")
    .writeExcel(file, sheetName = "happyPersons", keepFile = true)
// Add a new sheet to the previous file without replacing it, by setting keepFile = true -> Current sheets: allPersons, happyPersons, unhappyPersons
df.filter { person -> !person.isHappy }.remove("isHappy")
    .writeExcel(file, sheetName = "unhappyPersons", keepFile = true)

implementation("org.jetbrains.kotlinx:dataframe-arrow:$dataframe_version")

df.writeArrowIPC(file)
// or
df.writeArrowFeather(file)

val ipcByteArray: ByteArray = df.saveArrowIPCToByteArray()
// or
val featherByteArray: ByteArray = df.saveArrowFeatherToByteArray()

// Get schema from anywhere you want. It can be deserialized from JSON, generated from another dataset
// (including the DataFrame.columns().toArrowSchema() method), created manually, and so on.
val schema = Schema.fromJSON(schemaJson)

df.arrowWriter(

    // Specify your schema
    targetSchema = schema,

    // Specify desired behavior mode
    mode = ArrowWriter.Mode(
        restrictWidening = true,
        restrictNarrowing = true,
        strictType = true,
        strictNullable = false,
    ),

    // Specify mismatch subscriber
    mismatchSubscriber = writeMismatchMessage,

    ).use { writer: ArrowWriter ->

    // Save to any format and sink, like in the previous example
    writer.writeArrowFeather(file)
}