extend_se: Extend data by adding more columns.

In rquery: Relational Query Generator for Data Manipulation at Scale

Extend data by adding more columns.

Description

Create a node similar to a Codd extend relational operator (add derived columns).

Usage

extend_se(
  source,
  assignments,
  ...,
  partitionby = NULL,
  orderby = NULL,
  reverse = NULL,
  display_form = NULL,
  env = parent.frame()
)

Arguments

source	source to select from.
assignments	new column assignment expressions.
...	force later arguments to bind by name
partitionby	partitioning (window function) terms.
orderby	ordering (in window function) terms.
reverse	reverse ordering (in window function) terms.
display_form	chacter presentation form
env	environment to look for values in.

Details

Partitionby and orderby can only be used with a database that supports window-functions (such as PostgreSQL, Spark and so on).

Note: if any window/aggregation functions are present then at least one of partitionby or orderby must be non empty. For this purpose partitionby=1 is allowed and means "single partition on the constant 1."

Value

extend node.

Examples

if (requireNamespace("DBI", quietly = TRUE) && requireNamespace("RSQLite", quietly = TRUE)) {
  my_db <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
  d <- rq_copy_to(my_db, 'd',
                   data.frame(AUC = 0.6, R2 = 0.2))
  optree <- extend_se(d, c("v" %:=% "AUC + R2", "x" %:=% "pmax(AUC,v)"))
  cat(format(optree))
  sql <- to_sql(optree, my_db)
  cat(sql)
  print(DBI::dbGetQuery(my_db, sql))

  DBI::dbDisconnect(my_db)
}

rquery documentation built on Aug. 20, 2023, 9:06 a.m.