project data by grouping, and adding aggregate columns.

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


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)
}
#> mk_td("d", c(
#>   "group",
#>   "val")) %.>%
#>  project(., vmax := max(val),
#>   groupby = c('group'))
#> SELECT `group`, max ( `val` ) AS `vmax` FROM (
#>  SELECT
#>   `group`,
#>   `val`
#>  FROM
#>   `d`
#>  ) tsql_79879680555684161256_0000000000
#> GROUP BY
#>  `group`
#>   group vmax
#> 1     a    2
#> 2     b    4
#> mk_td("d", c(
#>   "group",
#>   "val")) %.>%
#>  project(., vmax := max(val),
#>   groupby = c())
#> SELECT max ( `val` ) AS `vmax` FROM (
#>  SELECT
#>   `val`
#>  FROM
#>   `d`
#>  ) tsql_54595027929007766507_0000000000
#>   vmax
#> 1    4