VJoin Tables

../../../../../_images/vjoin_table.svg

The operation of vertical join, or VJoin, stacks the columns from the incoming Tables that have the same name vertically upon each other, under the condition that they exist in all Tables. If the condition is fulfilled the number of rows in the outgoing Table will be equal to the sum of the number of rows in the incoming Tables. If there exist no overlap over all Tables the output will be an empty Table.

In the GUI it is possible to override the overlap requirement and let the node work in a state where the output will include all columns that exist the incoming Tables. The columns that do not exist in all Tables are, where they are missing, represented by dummy columns with the same length as the other columns in the considered Table. The dummy for a column with numerical values is filled with NaNs while for a column with strings the elements in the dummy consist of empty strings. This state is regulated by the “Complement missing columns”-checkbox.

An index column will be created in the outgoing Table if a name is specified for the column in the GUI, by default the index column has the name “VJoin-index”. In the index column, elements in the joined output that originate from the same incoming Table will be given the same index number. If one wants to do the reversed operation, VSplit Table, the index column is important. No index column will be created if the specified name is an empty string.

In the GUI it is also possible to specify the name of an incoming index column, a column with information about previous VJoin operations. If the specified index column exists in the incoming Tables the information of the previous join operations will be regarded when the new index column is constructed. The new index column will replace the old ones in the output of the node.

An increment will be applied to the outgoing index column if there exist incoming Tables with the number of rows equal to zero. The size of this increment can be specified in the GUI of the node, where default value is 0. The vertical join, or VJoin, is one of two operations that merge the content of a number of Tables into a new Table. The other operation in this category is the horizontal join, see HJoin Table to obtain more information.

class node_vjoin_tables.VJoinTablesNode[source]

Vertical join of Tables.

Opposite node:

VSplit Table

Ref. nodes:

VJoin Table, VJoin Tables pairwise

Inputs:
port1
: [table]

Input Tables

Outputs:
port1
: table

Joined Tables

Configuration:
Complement missing columns

Select if columns that are not represented in all Tables to be complemented

Complement strategy

When “Complement with nan or empty string” is selected missing columns will be replaced by columns of nan or empty strings. When “Mask missing values” is selected missing columns will be result in masked values

Increment in index column

Specify the increment in the outgoing index column at the existence of tables with the number of rows equal to zero.

Output index

Specify name for output index column. Can be left empty.