Implement projection operator.

Source: R/relop_project.R

data.table based implementation.

# S3 method for relop_project
ex_data_table_step(
  optree,
  ...,
  tables = list(),
  source_usage = NULL,
  source_limit = NULL,
  env = parent.frame()
)

Arguments

optree

relop operations tree.
...

not used, force later arguments to bind by name.
tables

named list map from table names used in nodes to data.tables and data.frames.
source_usage

list mapping source table names to vectors of columns used.
source_limit

if not null limit all table sources to no more than this many rows (used for debugging).
env

environment to work in.

Examples


dL <- build_frame(
  "subjectID", "surveyCategory"     , "assessmentTotal" |
    1          , "withdrawal behavior", 5                 |
    1          , "positive re-framing", 2                 |
    2          , "withdrawal behavior", 3                 |
    2          , "positive re-framing", 4                 )
test_p <- local_td(dL) %.>%
  project(.,
          maxscore := max(assessmentTotal),
          count := n(),
          groupby = 'subjectID')
cat(format(test_p))

#> mk_td("dL", c(
#>   "subjectID",
#>   "surveyCategory",
#>   "assessmentTotal")) %.>%
#>  project(., maxscore := max(assessmentTotal), count := n(),
#>   groupby = c('subjectID'))
dL %.>% test_p

#>   subjectID maxscore count
#> 1         1        5     2
#> 2         2        4     2