Build data.table implementation of lookup_by_column. We do this here as rqdatatable is a data.table aware package (and rquery is not).
make_dt_lookup_by_column(pick, result)
character scalar, name of column to control value choices.
character scalar, name of column to place values in.
f_dt() function.
df = data.frame(x = c(1, 2, 3, 4),
y = c(5, 6, 7, 8),
choice = c("x", "y", "x", "z"),
stringsAsFactors = FALSE)
make_dt_lookup_by_column("choice", "derived")(df)
#> x y choice derived
#> 1: 1 5 x 1
#> 2: 2 6 y 6
#> 3: 3 7 x 3
#> 4: 4 8 z NA
# # base-R implementation
# df %.>% lookup_by_column(., "choice", "derived")
# # # data.table implementation (requies rquery 1.1.0, or newer)
# # df %.>% lookup_by_column(., "choice", "derived",
# # f_dt_factory = rqdatatable::make_dt_lookup_by_column)