Add update{}.asFrame{} for ColumnGroup update.

Author: nikitinas

docs/StardustDocs/topics/update.md

@@ -8,12 +8,13 @@ Returns `DataFrame` with changed values in some cells. Column types can not be c
 update { columns }
     [.where { rowCondition } ]
     [.at(rowIndices) ] 
-     .with { rowExpression } | .notNull { rowExpression } | .perCol { colExpression } | .perRowCol { rowColExpression } | .withValue(value) | .withNull() | .withZero() 
+     .with { rowExpression } | .notNull { rowExpression } | .perCol { colExpression } | .perRowCol { rowColExpression } | .withValue(value) | .withNull() | .withZero() | .asFrame { frameExpression } 
 
 rowCondition: DataRow.(OldValue) -> Boolean
 rowExpression: DataRow.(OldValue) -> NewValue
 colExpression: DataColumn.(DataColumn) -> NewValue
 rowColExpression: DataRow.(DataColumn) -> NewValue
+frameExpression: DataFrame.(DataFrame) -> DataFrame
 ```
 
 See [column selectors](ColumnSelectors.md) and [row expressions](DataRow.md#row-expressions)
@@ -68,3 +69,13 @@ df.update { colsOf<String?>() }.perRowCol { row, col -> col.name() + ": " + row.
 ```
 
 <!---END-->
+
+Update [ColumnGroup](DataColumn.md#columngroup) as [DataFrame](DataFrame.md):
+
+<!---FUN updateAsFrame-->
+
+```kotlin
+df.update { name }.asFrame { select { lastName } }
+```
+
+<!---END-->

src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/update.kt

@@ -4,6 +4,8 @@ import org.jetbrains.kotlinx.dataframe.AnyRow
 import org.jetbrains.kotlinx.dataframe.ColumnsSelector
 import org.jetbrains.kotlinx.dataframe.DataColumn
 import org.jetbrains.kotlinx.dataframe.DataFrame
+import org.jetbrains.kotlinx.dataframe.DataFrameExpression
+import org.jetbrains.kotlinx.dataframe.DataRow
 import org.jetbrains.kotlinx.dataframe.RowColumnExpression
 import org.jetbrains.kotlinx.dataframe.RowValueExpression
 import org.jetbrains.kotlinx.dataframe.RowValueFilter
@@ -54,6 +56,9 @@ public infix fun <T, C> Update<T, C>.with(expression: UpdateExpression<T, C, C?>
         expression(row, value)
     }
 
+public infix fun <T, C, R> Update<T, DataRow<C>>.asFrame(expression: DataFrameExpression<C, DataFrame<R>>): DataFrame<T> =
+    df.replace(columns).with { it.asColumnGroup().let { expression(it, it) }.asColumnGroup(it.name()) }
+
 public fun <T, C> Update<T, C>.asNullable(): Update<T, C?> = this as Update<T, C?>
 
 public fun <T, C> Update<T, C>.perCol(values: Map<String, C>): DataFrame<T> = updateWithValuePerColumnImpl {

tests/src/test/kotlin/org/jetbrains/kotlinx/dataframe/samples/api/Modify.kt

@@ -34,6 +34,15 @@ class Modify : TestBase() {
         // SampleEnd
     }
 
+    @Test
+    fun updateAsFrame() {
+        val res =
+            // SampleStart
+            df.update { name }.asFrame { select { lastName } }
+            // SampleEnd
+        res shouldBe df.remove { name.firstName }
+    }
+
     @Test
     fun updatePerColumn() {
         val updated =

tests/src/test/kotlin/org/jetbrains/kotlinx/dataframe/testSets/person/DataFrameTreeTests.kt

@@ -14,7 +14,6 @@ import org.jetbrains.kotlinx.dataframe.api.GroupWithKey
 import org.jetbrains.kotlinx.dataframe.api.add
 import org.jetbrains.kotlinx.dataframe.api.addId
 import org.jetbrains.kotlinx.dataframe.api.after
-import org.jetbrains.kotlinx.dataframe.api.all
 import org.jetbrains.kotlinx.dataframe.api.append
 import org.jetbrains.kotlinx.dataframe.api.asColumnGroup
 import org.jetbrains.kotlinx.dataframe.api.asDataFrame