问题
If I extract a row from a dataframe, my custom s3 class stays:
test_df = iris
class(test_df) <- c("test_class", class(test_df))
class(test_df[1,])
[1] "test_class" "data.frame"
But this does not work for tibbles:
test_df <- as_tibble(test_df)
class(test_df) <- c("test_class", class(test_df))
class(test_df[1,])
[1] "tbl_df" "tbl" "data.frame"
Is there a way around this? Thanks
回答1:
The answer comes from the s3 section of Hadley's Advanced R book. You have to define a class constructor function and a new [
function.
new_test <- function(x, ...) {
structure(x, class = c("test_class", class(x)))
}
`[.test_class` <- function(x, ...) {
new_test(NextMethod())
}
test_df <- iris
test_df <- as_tibble(test_df)
class(test_df) <- c("test_class", class(test_df))
class(test_df[1,])
[1] "tbl_df" "tbl" "data.frame"
来源:https://stackoverflow.com/questions/54084280/row-subsets-of-tibble-loses-custom-s3-class