Package tech.tablesaw.aggregate

Class Summarizer

java.lang.Object

tech.tablesaw.aggregate.Summarizer

public class Summarizer
extends Object

Summarizes the data in a table, by applying functions to a subset of its columns.

How to use:

1. Create an instance providing a source table, the column or columns to summarize, and a function or functions to apply 2. Applying the functions to the designated columns, possibly creating subgroup summaries using one of the by() methods

Constructor Summary

Constructors

Constructor	Description
Summarizer(Table sourceTable, List<String> columnNames, AggregateFunction<?,?>... functions)	Returns an object capable of summarizing the given column in the given sourceTable, by applying the given functions
Summarizer(Table sourceTable, Column<?> column, AggregateFunction<?,?>... functions)	Returns an object capable of summarizing the given column in the given sourceTable, by applying the given functions
Summarizer(Table sourceTable, Column<?> column1, Column<?> column2, AggregateFunction<?,?>... functions)	Returns an object capable of summarizing the given columns in the given sourceTable, by applying the given functions
Summarizer(Table sourceTable, Column<?> column1, Column<?> column2, Column<?> column3, AggregateFunction<?,?>... functions)	Returns an object capable of summarizing the given column2 in the given sourceTable, by applying the given functions
Summarizer(Table sourceTable, Column<?> column1, Column<?> column2, Column<?> column3, Column<?> column4, AggregateFunction<?,?>... functions)	Returns an object capable of summarizing the given columns in the given sourceTable, by applying the given functions

Method Summary

Modifier and Type	Method	Description
Table	apply()	Returns the result of applying to the functions to all the values in the appropriate column TODO add a test that uses a non numeric return type with apply
Table	by(int step)	Returns a summary of the records grouped into subsets of the same size, in the order they appear
Table	by(String... columnNames)	Similar in intent to the SQL "group by" statement, it produces a table with one row for each subgroup of the output data containing the result of applying the summary functions to the subgroup
Table	by(CategoricalColumn<?>... columns)	Similar in intent to the SQL "group by" statement, it produces a table with one row for each subgroup of the output data containing the result of applying the summary functions to the subgroup
Summarizer	groupBy(int step)	TODO: research how the groupBy() methods differ from the by() methods? Are they synonyms?
Summarizer	groupBy(String... columnNames)	TODO: research how the groupBy() methods differ from the by() methods? Are they synonyms?
Summarizer	groupBy(CategoricalColumn<?>... columns)	TODO: research how the groupBy() methods differ from the by() methods? Are they synonyms?
Table	having(Function<Table,Selection> selection)	Similar in intent to the SQL having command, it enables the user to apply a filter to the grouped results of summary.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Summarizer

public Summarizer(Table sourceTable,
                  Column<?> column,
                  AggregateFunction<?,?>... functions)

Returns an object capable of summarizing the given column in the given sourceTable, by applying the given functions

Summarizer

public Summarizer(Table sourceTable,
                  List<String> columnNames,
                  AggregateFunction<?,?>... functions)

Returns an object capable of summarizing the given column in the given sourceTable, by applying the given functions

Summarizer

public Summarizer(Table sourceTable,
                  Column<?> column1,
                  Column<?> column2,
                  AggregateFunction<?,?>... functions)

Returns an object capable of summarizing the given columns in the given sourceTable, by applying the given functions

Summarizer

public Summarizer(Table sourceTable,
                  Column<?> column1,
                  Column<?> column2,
                  Column<?> column3,
                  Column<?> column4,
                  AggregateFunction<?,?>... functions)

Returns an object capable of summarizing the given columns in the given sourceTable, by applying the given functions

Summarizer

public Summarizer(Table sourceTable,
                  Column<?> column1,
                  Column<?> column2,
                  Column<?> column3,
                  AggregateFunction<?,?>... functions)

Returns an object capable of summarizing the given column2 in the given sourceTable, by applying the given functions

Method Detail

by

public Table by(String... columnNames)

Similar in intent to the SQL "group by" statement, it produces a table with one row for each subgroup of the output data containing the result of applying the summary functions to the subgroup

Parameters:

columnNames - The names of the columns to group on

Returns:

A table containing the grouped results

by

public Table by(CategoricalColumn<?>... columns)

Similar in intent to the SQL "group by" statement, it produces a table with one row for each subgroup of the output data containing the result of applying the summary functions to the subgroup

Parameters:

columns - The columns to group on

Returns:

A table containing the grouped results

by

public Table by(int step)

Returns a summary of the records grouped into subsets of the same size, in the order they appear

All groups have the same number of records. If the final group has fewer than step records it is dropped.

Parameters:

step - the number or records to include in each group

apply

public Table apply()

Returns the result of applying to the functions to all the values in the appropriate column TODO add a test that uses a non numeric return type with apply

having

public Table having(Function<Table,Selection> selection)

Similar in intent to the SQL having command, it enables the user to apply a filter to the grouped results of summary. Only groups that pass the filter are included in the output.

Parameters:

selection - A Selection where each index provided refers to a row in the output table

Returns:

A table of filtered summarized data

groupBy

public Summarizer groupBy(CategoricalColumn<?>... columns)

TODO: research how the groupBy() methods differ from the by() methods? Are they synonyms?

groupBy

public Summarizer groupBy(String... columnNames)

TODO: research how the groupBy() methods differ from the by() methods? Are they synonyms?

groupBy

public Summarizer groupBy(int step)

TODO: research how the groupBy() methods differ from the by() methods? Are they synonyms?