cdm_zoom_to_tbl: Single out a table of a `dm`

Description

Zooming to a table of a dm allows for the use of many dplyr-verbs directly on this table, while retaining the context of the dm object.

Usage

cdm_zoom_to_tbl(dm, table)
cdm_insert_zoomed_tbl(
  dm,
  new_tbl_name = NULL,
  repair = "unique",
  quiet = FALSE
)
cdm_update_zoomed_tbl(dm)
cdm_zoom_out(dm)

Arguments

A dm object.

table

A table in the dm.

new_tbl_name

Name of the new table.

repair

Either a string or a function. If a string, it must be one of "check_unique", "minimal", "unique", or "universal". If a function, it is invoked with a vector of minimal names and must return minimal names, otherwise an error is thrown.

Minimal names are never NULL or NA. When an element doesn't have a name, its minimal name is an empty string.
Unique names are unique. A suffix is appended to duplicate names to make them unique.
Universal names are unique and syntactic, meaning that you can safely use the names as variables without causing a syntax error.

The "check_unique" option doesn't perform any name repair. Instead, an error is raised if the names don't suit the "unique" criteria.

quiet

By default, the user is informed of any renaming caused by repairing the names. This only concerns unique and universal repairing. Set quiet to TRUE to silence the messages.

Details

cdm_zoom_to_tbl(): zooms to the given table.

cdm_update_zoomed_tbl(): overwrites the originally zoomed table with the manipulated table. The filter conditions for the zoomed table are added to the original filter conditions.

cdm_insert_zoomed_tbl(): adds a new table to the dm.

cdm_zoom_out(): discards the zoomed table and returns the dm as it was before zooming.

Whenever possible, the key relations of the original table are transferred to the resulting table when using cdm_insert_zoomed_tbl() or cdm_update_zoomed_tbl().

Functions from dplyr that are supported for a zoomed_dm: group_by(), summarise(), mutate(), transmute(), select(), rename() and ungroup(). You can use these functions just like you would with a normal table.

filter() is also supported, but treated in a special way: the filter expression for the zoomed table is stored in the dm and is treated in a way that depends on which function you use to return to a normal dm:

cdm_zoom_out(): all filter conditions for the zoomed table are discarded
cdm_update_zoomed_tbl(): the filter conditions of the original table and those of the zoomed table are combined
cdm_insert_zoomed_tbl(): the filter conditions of the original table stay there and those of the zoomed table are transferred to the new table of the dm