init research

dataframe/docs/StardustDocs/topics/map.md

@@ -0,0 +1,95 @@
+[//]: # (title: map)
+
+<!---IMPORT org.jetbrains.kotlinx.dataframe.samples.api.Modify-->
+
+Creates [`List`](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/-list/), [DataFrame](DataFrame.md) or [DataColumn](DataColumn.md) 
+with values computed from rows of original [DataFrame](DataFrame.md).
+
+**Related operations**: [](addRemove.md)
+
+**Map into `List`:**
+
+```text
+map { rowExpression }: List<T>
+
+rowExpression: DataRow.(DataRow) -> Value
+```
+
+<!---FUN map-->
+
+```kotlin
+df.map { 2021 - it.age }
+```
+
+<!---END-->
+
+**Map into `DataColumn`:**
+
+```text
+mapToColumn(columnName) { rowExpression }: DataColumn
+
+rowExpression: DataRow.(DataRow) -> Value
+```
+
+<!---FUN mapToColumn-->
+<tabs>
+<tab title="Properties">
+
+```kotlin
+df.mapToColumn("year of birth") { 2021 - age }
+```
+
+</tab>
+<tab title="Strings">
+
+```kotlin
+df.mapToColumn("year of birth") { 2021 - "age"<Int>() }
+```
+
+</tab></tabs>
+<!---END-->
+
+See [row expressions](DataRow.md#row-expressions)
+
+**Map into [`DataFrame`](DataFrame.md):**
+
+```kotlin
+mapToFrame { 
+    columnMapping
+    columnMapping
+    ...
+} : DataFrame
+
+columnMapping = column into columnName | columnName from column | columnName from { rowExpression } | +column  
+```
+
+<!---FUN mapMany-->
+<tabs>
+<tab title="Properties">
+
+```kotlin
+df.mapToFrame {
+    "year of birth" from { 2021 - age }
+    expr { age > 18 } into "is adult"
+    name.lastName.map { it.length } into "last name length"
+    "full name" from { name.firstName + " " + name.lastName }
+    +city
+}
+```
+
+</tab>
+<tab title="Strings">
+
+```kotlin
+df.mapToFrame {
+    "year of birth" from { 2021 - "age"<Int>() }
+    expr { "age"<Int>() > 18 } into "is adult"
+    "name"["lastName"]<String>().map { it.length } into "last name length"
+    "full name" from { "name"["firstName"]<String>() + " " + "name"["lastName"]<String>() }
+    +"city"
+}
+```
+
+</tab></tabs>
+<inline-frame src="resources/org.jetbrains.kotlinx.dataframe.samples.api.Modify.mapMany.html" width="100%"/>
+<!---END-->