rquery (version 1.4.99)

project: project data by grouping, and adding aggregate columns.

Description

Supports bquote() .()-style name abstraction including .(-) notation to promote strings to names (please see here: https://github.com/WinVector/rquery/blob/master/Examples/Substitution/Substitution.md).

Usage

project(source, ..., groupby = c(), env = parent.frame())
project_nse(source, ..., groupby = c(), env = parent.frame())
aggregate_nse(source, ..., groupby = c(), env = parent.frame())

Value

project node.

Arguments

source

source to select from.

...

new column assignment expressions.

groupby

grouping columns.

env

environment to look for values in.

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(group = c('a', 'a', 'b', 'b'),
               val = 1:4,
               stringsAsFactors = FALSE))

  op_tree <- d %.>%
    project(., groupby = "group", vmax %:=% max(val))
  cat(format(op_tree))
  sql <- to_sql(op_tree, my_db)
  cat(sql)
  execute(my_db, op_tree) %.>%
     print(.)

  op_tree <- d %.>%
    project(., groupby = NULL, vmax %:=% max(val))
  cat(format(op_tree))
  sql <- to_sql(op_tree, my_db)
  cat(sql)
  execute(my_db, op_tree) %.>%
    print(.)

  DBI::dbDisconnect(my_db)
}