rquery (version 0.5.0)

extend_se: 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, 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.

env

environment to look for values in.

Value

extend node.

Details

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

Examples

# NOT RUN {
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))

  # SQLite can not run the following query
  optree2 <- extend_se(d, "v" %:=% "rank()",
                    partitionby = "AUC", orderby = "R2")
  sql2 <- to_sql(optree2, my_db)
  cat(sql2)

  DBI::dbDisconnect(my_db)
}

# }