dm (version 0.0.4)

dm: Data model class

Description

The dm class wraps dplyr::src and adds a description of table relationships inspired by datamodelr, of which it also borrows code.

dm() coerces its inputs. If called without arguments, an empty dm object is created.

new_dm() only checks if the inputs are of the correct class. If called without arguments, an empty dm object is created.

validate_dm() checks consistency between the dplyr source and the datamodelr based specification of table relationships. This function is currently a no-op.

cdm_get_src() returns the dplyr source component of a dm object.

cdm_get_con() returns the connection object (con-part of dplyr source component) of a dm object.

cdm_get_tables() returns a named list with dplyr tbl objects of a dm object. The filter expressions are NOT evaluated at this stage. To get the filtered tables, use tbl.dm()

cdm_get_filter() returns the filter component of a dm object, the set filter expressions.

is_dm() returns TRUE if the input is of class dm.

as_dm() coerces objects to the dm class

Usage

dm(src, data_model = NULL)
new_dm(tables, data_model)
validate_dm(x)
cdm_get_src(x)
cdm_get_con(x)
cdm_get_tables(x)
cdm_get_filter(x)
is_dm(x)
as_dm(x)

Arguments

src

A dplyr table source object.

data_model

A datamodelr data model object, or NULL.

tables

A list of the tables (tibble-objects, not names) to be included in the dm object

x

An object.

See Also

• cdm_add_pk() and cdm_add_fk() add primary and foreign keys

• cdm_copy_to() and cdm_learn_from_db() for DB interaction

• cdm_draw() for visualization

• cdm_join_to_tbl() for flattening

• cdm_filter() for filtering

• cdm_select_tbl() for creating a dm with only a subset of the tables

• decompose_table() as one example of the table surgery family

• check_key() and check_if_subset() for checking for key properties

• check_cardinality() for checking the cardinality of the relation between two tables

• cdm_nycflights13() for creating an example dm object

Examples

# NOT RUN {
library(dplyr)
dm(dplyr::src_df(pkg = "nycflights13"))
as_dm(list(iris = iris, mtcars = mtcars))

cdm_nycflights13() %>% tbl("airports")
cdm_nycflights13() %>% src_tbls()
cdm_nycflights13() %>% cdm_get_src()
cdm_nycflights13() %>% cdm_get_tables()

cdm_nycflights13() %>%
  cdm_rename_tbl(ap = airports)
cdm_nycflights13() %>%
  cdm_rename_tbl(ap = airports, fl = flights)
# }