Tibbles are S3 objects of class
c("tbl_df", "tbl", "data.frame"). This means that they
inherit their behavior from the "data.frame" class and add
two subclasses "tbl" and "tbl_df". The pillar
and tibble packages provide methods for "tbl" and
"tbl_df", respectively. Package authors and programmers can
implement subclasses that extend either "tbl_df" (and its
subclasses) or only "tbl" to provide custom behavior for
tibble-like objects. In addition, vectors classes can be implemented
from scratch or on top of existing classes, to be used as columns. This
article provides links to the various customization points that help you
avoiding reimplement existing behavior, and describes the difference
between "tbl" and "tbl_df".
Read more in the second edition of Advanced R:
Change or tweak the way a tibble prints:
vignette("extending", package = "pillar")
Change or tweak the way a column type is printed in a tibble:
vignette("pillar", package = "vctrs")
Implement a new column data type:
vignette("s3-vector", package = "vctrs")
Making your tibble subclass work well with dplyr:
?dplyr::dplyr_extending
library(tibble)For tibble >= 3.0.0, the "tbl" class is responsible
for printing, while the "tbl_df" class adds tibble’s sturdy
subsetting and subset assignment behavior (see
vignette("invariants") for details). This means that a data
frame class that would like to (mostly) print like a tibble but keep the
behavior from base R’s data frames can inherit from
c("tbl", "data.frame") or just from "tbl". An
example is the "tbl_sql" class in the dbplyr package that
is used to implement lazy database tables.
my_tbl_df <- new_tibble(
list(a = 1:3, b = 2:4),
class = "my_tbl_df"
)
tbl_sum.my_tbl_df <- function(x, ...) {
c(
"My custom tibble" = "Some info about it",
NextMethod()
)
}
my_tbl_df## # My custom tibble: Some info about it
## # A tibble: 3 × 2
## a b
## <int> <int>
## 1 1 2
## 2 2 3
## 3 3 4my_tbl_df[, "a"]## # My custom tibble: Some info about it
## # A tibble: 3 × 1
## a
## <int>
## 1 1
## 2 2
## 3 3my_tbl <- vctrs::new_data_frame(
list(a = 1:3, b = 2:4),
class = c("my_tbl", "tbl")
)
tbl_sum.my_tbl <- function(x, ...) {
c(
"My custom data frame" = "Some info about it",
NextMethod()
)
}
my_tbl## # My custom data frame: Some info about it
## # A data frame: 3 × 2
## a b
## <int> <int>
## 1 1 2
## 2 2 3
## 3 3 4my_tbl[, "a"]## [1] 1 2 3