rquery (version 1.4.99)

extend: Extend data by adding more columns.

Description

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

Usage

extend(
  source,
  ...,
  partitionby = NULL,
  orderby = NULL,
  reverse = NULL,
  display_form = NULL,
  env = parent.frame()
)
extend_nse(
  source,
  ...,
  partitionby = NULL,
  orderby = NULL,
  reverse = NULL,
  display_form = NULL,
  env = parent.frame()
)

Value

extend node.

Arguments

source

source to select from.

...

new column assignment expressions.

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).

Supports bquote() .()-style name abstraction with the extenson that - promotes strings to names (please see here: https://github.com/WinVector/rquery/blob/master/Examples/Substitution/Substitution.md).

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."

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))
  NEWCOL <- as.name("v")
  NEWVALUE = "zz"
  optree <- extend(d, .(NEWCOL) %:=% ifelse(AUC>0.5, R2, 1.0), .(NEWVALUE) %:=% 6)
  cat(format(optree))
  sql <- to_sql(optree, my_db)
  cat(sql)
  print(DBI::dbGetQuery(my_db, sql))
  DBI::dbDisconnect(my_db)
}