rquery (version 1.4.6)

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()
)

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.

Value

extend node.

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

# 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))
  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)
}

# }

Run the code above in your browser using DataCamp Workspace