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

extend_se(
  source,
  assignments,
  ...,
  partitionby = NULL,
  orderby = NULL,
  reverse = NULL,
  display_form = NULL,
  env = parent.frame()
)

Arguments

source

source to select from.

assignments

new column assignment expressions.

...

force later arguments to bind by name

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).

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)) optree <- extend_se(d, c("v" %:=% "AUC + R2", "x" %:=% "pmax(AUC,v)")) cat(format(optree)) sql <- to_sql(optree, my_db) cat(sql) print(DBI::dbGetQuery(my_db, sql)) DBI::dbDisconnect(my_db) }
#> mk_td("d", c( #> "AUC", #> "R2")) %.>% #> extend(., #> v := AUC + R2) %.>% #> extend(., #> x := pmax(AUC, v)) #> SELECT #> `AUC`, #> `R2`, #> `v`, #> ( CASE WHEN ( `AUC` ) IS NULL THEN ( `v` ) WHEN ( `v` ) IS NULL THEN ( `AUC` ) WHEN ( `AUC` ) >= ( `v` ) THEN ( `AUC` ) ELSE ( `v` ) END ) AS `x` #> FROM ( #> SELECT #> `AUC`, #> `R2`, #> `AUC` + `R2` AS `v` #> FROM ( #> SELECT #> `AUC`, #> `R2` #> FROM #> `d` #> ) tsql_19673537631902327278_0000000000 #> ) tsql_19673537631902327278_0000000001 #> AUC R2 v x #> 1 0.6 0.2 0.8 0.8