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dataframe/docs/StardustDocs/topics/modify.md

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+[//]: # (title: Modify)
+<show-structure depth="3"/>
+
+<tip> 
+
+[`DataFrame`](DataFrame.md) object is immutable and all operations return a new instance of [`DataFrame`](DataFrame.md).
+
+</tip>
+
+## Naming conventions
+
+[`DataFrame`](DataFrame.md) is a columnar data structure and is more oriented to column-wise operations. Most transformation operations start with [column selector](ColumnSelectors.md) that selects target columns for the operation.
+Syntax of most column operations assumes that they are applied to columns, so they don't include word `column` in their naming.    
+
+On the other hand, the Kotlin DataFrame library follows `Koltin Collections` naming for row-wise operations 
+as [`DataFrame`](DataFrame.md) can be interpreted as a [`Collection`](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/) of rows. The slight naming difference with `Kotlin Collection` is that all operations are named in imperative way: `sortBy`, `shuffle` etc. 
+
+**Pairs of column/row operations:**
+* [add](add.md) columns / [append](append.md) rows
+* [remove](remove.md) columns / [drop](drop.md) rows
+* [select](select.md) columns / [filter](filter.md) rows
+* [group](group.md) columns / [groupBy](groupBy.md) for rows
+* [reorder](reorder.md) columns / [sortBy](sortBy.md) for rows
+* [join](join.md) to unite columns / [concat](concat.md) to unite rows
+
+**Horizontal (column) operations:**
+* [add](add.md) — add columns
+* [addId](add.md#addid) — add `id` column
+* [flatten](flatten.md) — remove column groupings recursively
+* [group](group.md) — group columns into [`ColumnGroup`](DataColumn.md#columngroup)
+* [insert](insert.md) — insert column
+* [map](map.md) — map columns into new [`DataFrame`](DataFrame.md) or [`DataColumn`](DataColumn.md)
+* [merge](merge.md) — merge several columns into one
+* [move](move.md) — move columns or change column groupings
+* [remove](remove.md) — remove columns
+* [rename](rename.md) — rename columns
+* [reorder](reorder.md) — reorder columns
+* [replace](replace.md) — replace columns
+* [select](select.md) — select subset of columns
+* [split](split.md) — split values into new columns
+* [ungroup](ungroup.md) — remove column grouping
+
+**Vertical (row) operations:**
+* [append](append.md) — add rows
+* [concat](concat.md) — union rows from several [`DataFrame`](DataFrame.md) objects
+* [distinct](distinct.md) / [distinctBy](distinct.md#distinctby) — remove duplicated rows
+* [drop](drop.md) / [dropLast](sliceRows.md#droplast) / [dropWhile](sliceRows.md#dropwhile) / [dropNulls](drop.md#dropnulls) / [dropNA](drop.md#dropna) — remove rows by condition
+* [duplicate](duplicate.md) — duplicate rows 
+* [explode](explode.md) — spread lists and [`DataFrame`](DataFrame.md) objects vertically into new rows
+* [filter](filter.md) / [filterBy](filter.md#filterby) — filter rows
+* [implode](implode.md) — merge column values into lists grouping by other columns
+* [reverse](reverse.md) — reverse rows 
+* [shuffle](shuffle.md) — reorder rows randomly
+* [sortBy](sortBy.md) / [sortByDesc](sortBy.md#sortbydesc) / [sortWith](sortBy.md#sortwith) — sort rows
+* [split](split.md) — split values into new rows
+* [take](sliceRows.md#take) / [takeLast](sliceRows.md#takelast) / [takeWhile](sliceRows.md#takewhile) — get first/last rows
+
+**Value modification:**
+* [convert](convert.md) — convert values into new types
+* [parse](parse.md) — try to convert `String` values into appropriate types
+* [unfold](unfold.md) — convert / "unfold" objects to [`ColumnGroup`](DataColumn.md#columngroup)
+* [update](update.md) — update values preserving column types
+* [fillNulls](fill.md#fillnulls) / [fillNaNs](fill.md#fillnans) / [fillNA](fill.md#fillna) — replace missing values
+
+**Reshaping:**
+* [pivot](pivot.md) / [pivotCounts](pivot.md#pivotcounts) / [pivotMatches](pivot.md#pivotmatches) — convert values into new columns
+* [gather](gather.md) — convert pairs of column names and values into `key` and `value` columns
+
+**Learn how to:**
+* [Slice rows](sliceRows.md)
+* [Select columns](select.md)
+* [Filter rows](filterRows.md)
+* [Reorder rows](reorderRows.md)
+* [Group/concat rows](groupByConcat.md)
+* [Update/convert values](updateConvert.md)
+* [Split/merge values](splitMerge.md)
+* [Add/map/remove columns](addRemove.md)
+* [Move/rename columns](moveRename.md)
+* [Group/ungroup/flatten columns](groupUngroupFlatten.md)
+* [Insert/replace columns](insertReplace.md)
+* [Explode/implode columns](explodeImplode.md)
+* [Pivot/gather columns](pivotGather.md)
+* [Append values](append.md)
+* [Adjust schema](adjustSchema.md)