Both single element subsetting via [[ and $, as well as multi-element
subsetting via [ are available for prt objects. Subsetting semantics
are modeled after those of the tibble class with the main difference
being that there tibble returns tibble objects, prt returns
data.tables. Differences to base R include that partial column name
matching for $ is not allowed and coercion to lower dimensions for
[ is always disabled by default. As prt objects are immutable, all
subset-replace functions ([[<-, $<- and [<-) yield an error when
passed a prt object.
# S3 method for prt
[[(x, i, j, ..., exact = TRUE)
# S3 method for prt
$(x, name)
# S3 method for prt
[(x, i, j, drop = FALSE)A prt object.
Row/column indexes. If j is omitted, i is used as column
index.
Generic compatibility: any further arguments are ignored.
Generic compatibility: only the default value of TRUE is
supported.
A literal character string or a name (possibly backtick quoted).
Coerce to a vector if fetching one column via tbl[, j].
Default FALSE, ignored when accessing a column via tbl[j].
dat <- as_prt(mtcars)
identical(dat$mpg, dat[["mpg"]])
#> [1] TRUE
dat$mp
#> Warning: Unknown or uninitialised column: `mp`.
#> NULL
mtcars$mp
#> [1] 21.0 21.0 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 17.8 16.4 17.3 15.2 10.4
#> [16] 10.4 14.7 32.4 30.4 33.9 21.5 15.5 15.2 13.3 19.2 27.3 26.0 30.4 15.8 19.7
#> [31] 15.0 21.4
identical(dim(dat["mpg"]), dim(mtcars["mpg"]))
#> [1] TRUE
identical(dim(dat[, "mpg"]), dim(mtcars[, "mpg"]))
#> [1] FALSE
identical(dim(dat[1L, ]), dim(mtcars[1L, ]))
#> [1] TRUE