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dataframe/docs/StardustDocs/topics/flatten.md

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+[//]: # (title: flatten)
+
+<!---IMPORT org.jetbrains.kotlinx.dataframe.samples.api.Modify-->
+
+Returns [`DataFrame`](DataFrame.md) without column groupings under selected columns.
+
+```text
+flatten  [ { columns } ]
+```
+
+Columns will keep their original names after flattening.
+Potential column name clashes are resolved by adding minimal possible name prefix from ancestor columns.
+
+**Related operations**: [](groupUngroupFlatten.md)
+
+See [column selectors](ColumnSelectors.md) for how to select the columns for this operation.
+
+<!---FUN flatten-->
+<tabs>
+<tab title="Properties">
+
+```kotlin
+// name.firstName -> firstName
+// name.lastName -> lastName
+df.flatten { name }
+```
+
+</tab>
+<tab title="Strings">
+
+```kotlin
+// name.firstName -> firstName
+// name.lastName -> lastName
+df.flatten("name")
+```
+
+</tab></tabs>
+<inline-frame src="resources/org.jetbrains.kotlinx.dataframe.samples.api.Modify.flatten.html" width="100%"/>
+<!---END-->
+
+To remove all column groupings in [`DataFrame`](DataFrame.md), invoke `flatten` without parameters:
+
+<!---FUN flattenAll-->
+
+```kotlin
+df.flatten()
+```
+
+<inline-frame src="resources/org.jetbrains.kotlinx.dataframe.samples.api.Modify.flattenAll.html" width="100%"/>
+<!---END-->