Operations

Multiplex operations

Simple operations (such as filter or select) return new DataFrame immediately, while more complex operations return an intermediate object that is used for further configuration of the operation. Let's call such operations multiplex.

Every multiplex operation configuration consists of:

• column selector that is used to select target columns for the operation

• additional configuration functions

• terminal function that returns modified DataFrame

Most multiplex operations end with into or with function. The following naming convention is used:

• into defines column names for storing operation results. Used in move, group, split, merge, gather, groupBy, rename.

• with defines row-wise data transformation with row expression. Used in update, convert, replace, pivot.

List of DataRow operations

• index(): Int — sequential row number in DataFrame, starts from 0

• prev(): DataRow? — previous row (null for the first row)

• next(): DataRow? — next row (null for the last row)

• diff(T) { rowExpression }: T / diffOrNull { rowExpression }: T? — difference between the results of a row expression calculated for current and previous rows

• explode(columns): DataFrame<T> — spread lists and DataFrame objects vertically into new rows

• values(): List<Any?> — list of all cell values from the current row

• valuesOf<T>(): List<T> — list of values of the given type

• columnsCount(): Int — number of columns

• columnNames(): List<String> — list of all column names

• columnTypes(): List<KType> — list of all column types

• namedValues(): List<NameValuePair<Any?>> — list of name-value pairs where name is a column name and value is cell value

• namedValuesOf<T>(): List<NameValuePair<T>> — list of name-value pairs where value has given type

• transpose(): DataFrame<NameValuePair<*>> — DataFrame of two columns: name: String is column names and value: Any? is cell values

• transposeTo<T>(): DataFrame<NameValuePair<T>> — DataFrame of two columns: name: String is column names and value: T is cell values

• getRow(Int): DataRow — row from DataFrame by row index

• getRows(Iterable<Int>): DataFrame — DataFrame with subset of rows selected by absolute row index.

• relative(Iterable<Int>): DataFrame — DataFrame with subset of rows selected by relative row index: relative(-1..1) will return previous, current and next row. Requested indices will be coerced to the valid range and invalid indices will be skipped

• getValue<T>(columnName) — cell value of type T by this row and given columnName

• getValueOrNull<T>(columnName) — cell value of type T? by this row and given columnName or null if there's no such column

• get(column): T — cell value by this row and given column

• String.invoke<T>(): T — cell value of type T by this row and given this column name

• ColumnPath.invoke<T>(): T — cell value of type T by this row and given this column path

• ColumnReference.invoke(): T — cell value of type T by this row and given this column

• df() — DataFrame that current row belongs to

List of DataRow statistics

The following statistics are available for DataRow:

• rowSum

• rowMean

• rowStd

These statistics will be applied only to values of appropriate types, and incompatible values will be ignored. For example, if a dataframe has columns of types String and Int, rowSum() will compute the sum of the Int values in the row and ignore String values.

To apply statistics only to values of a particular type use -Of versions:

• rowSumOf<T>

• rowMeanOf<T>

• rowStdOf<T>

• rowMinOf<T>

• rowMaxOf<T>

• rowMedianOf<T>

• rowPercentileOf<T>

List of DataFrame operations

• add — add columns

• addId — add id column

• append — add rows

• columns/columnNames/columnTypes — get list of top-level columns, column names or column types

• columnsCount — number of top-level columns

• concat — union rows from several DataFrame objects

• convert — change column values and/or column types

• corr — pairwise correlation of columns

• count — number of rows that match condition

• countDistinct — number of unique rows

• cumSum — cumulative sum of column values

• describe — basic column statistics

• distinct/distinctBy — remove duplicated rows

• drop/dropLast/dropWhile/dropNulls/dropNA/dropNaNs — remove rows by condition

• duplicate — duplicate rows

• explode — spread lists and DataFrame objects vertically into new rows

• fillNulls/fillNaNs/fillNA — replace missing values

• filter/filterBy — filter rows by condition

• first/firstOrNull — find first row by condition

• flatten — remove column groupings recursively

• forEachRow/forEachColumn — iterate over rows or columns

• format — conditional formatting for cell rendering

• gather — convert pairs of column names and values into new columns

• getColumn/getColumnOrNull/getColumnGroup/getColumns — get one or several columns

• group — group columns into ColumnGroup

• groupBy — group rows by key columns

• head — get first 5 rows of DataFrame

• implode — collapse column values into lists grouping by other columns

• inferType — infer column type from column values

• insert — insert column

• join — join two DataFrame objects by key columns

• joinWith — join two DataFrame object by an expression that evaluates joined DataRows to Boolean

• last/lastOrNull — find last row by condition

• map — map columns into new DataFrame or DataColumn

• max/maxBy/maxOf/maxFor — max of values

• mean/meanOf/meanFor — average of values

• median/medianOf/medianFor — median of values

• merge — merge several columns into one

• min/minBy/minOf/minFor — min of values

• move — move columns or change column groupings

• parse — try to convert strings into other types

• pivot/pivotCounts/pivotMatches — convert values into new columns

• remove — remove columns

• rename — rename columns

• reorder/reorderColumnsBy/reorderColumnsByName — reorder columns

• replace — replace columns

• reverse — reverse rows

• rows/rowsReversed — get rows in direct or reversed order

• rowsCount — number of rows

• schema — schema of columns: names, types and hierarchy

• select — select subset of columns

• shuffle — reorder rows randomly

• single/singleOrNull — get single row by condition

• sortBy/sortByDesc/sortWith — sort rows

• split — split column values into new rows/columns or inplace into lists

• std/stdOf/stdFor — standard deviation of values

• sum/sumOf/sumFor — sum of values

• take/takeLast/takeWhile — get first/last rows

• toList/toListOf — export DataFrame into a list of data classes

• toMap — export DataFrame into a map from column names to column values

• unfold - unfold objects (normal class instances) in columns according to their properties

• ungroup — remove column groupings

• update — update column values preserving column types

• values — Sequence of values traversed by row or by column

• valueCounts — counts for unique values

• xs — slice DataFrame by given key values

Shortcut operations

Some operations are shortcuts for more general operations:

• rename, group, flatten are special cases of move

• valueCounts is a special case of groupBy

• pivotCounts, pivotMatches are special cases of pivot

• fillNulls, fillNaNs, fillNA are special cases of update

• convert is a special case of replace

You can use these shortcuts to apply the most common DataFrame transformations easier, but you can always fall back to general operations if you need more customization.