To create a new class of projectable_col vectors, one simply needs to
define a col_*() helper function. This can be done with the new_col()
constructor function. The first field passed into the new_col() function
via the ... argument will be taken as the face value. This can be overriden
by explicitly defining a face_value() method. The subclass of the
projectable_col created in this way will be projectable_col_* where *
is replaced by whatever is passed in as the class argument.
new_col(..., shadow = character(), class)Fields to store in the projectable_col
A shadow to initialise the projectable_col with
A character vector giving the projectable_col subclass.
A projectable_col vector with subclass projectable_col_* where
* is given by whatever was passed in as the class argument.
# Define a `col_student` helper function:
col_student <- function(name = character(), age = integer(), grade = double()) {
new_col(name = name, age = age, grade = grade, class = "student")
}
col_student(c("Kinto", "Pinto"), c(25, 100), c(99, 100))
#> <col_student[2]>
#> [1] Kinto Pinto
# Define a `col_fivenum` helper function:
col_fivenum <- function(x, na.rm = TRUE) {
five_num <- fivenum(x, na.rm)
new_col(
median = five_num[3],
min = five_num[1],
hinge_lower = five_num[2],
hinge_upper = five_num[4],
max = five_num[5],
class = "fivenum"
)
}
library(dplyr)
iris %>%
group_by(Species) %>%
summarise(across(where(is.numeric), col_fivenum))
#> # A tibble: 3 × 5
#> Species Sepal.Length Sepal.Width Petal.Length Petal.Width
#> <fct> <col_fvnm> <col_fvnm> <col_fvnm> <col_fvnm>
#> 1 setosa 5 3.4 1.5 0.2
#> 2 versicolor 5.9 2.8 4.4 1.3
#> 3 virginica 6.5 3 5.6 2