rquery (version 1.4.6)

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

Description

project data by grouping, and adding aggregate columns.

Usage

project_se(source, assignments, ..., groupby = c(), env = parent.frame())
aggregate_se(source, assignments, ..., groupby = c(), env = parent.frame())

Arguments

source

source to select from.

assignments

new column assignment expressions.

...

not used, force later arguments to be by name

groupby

grouping columns.

env

environment to look for values in.

Value

project node.

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

  op_tree <- d %.>%
    project_se(., 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_se(., 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)
}

# }