as.data.table should remove extra attributes from extended data.frames

Spotted when investigating #5698

x = iris
class(x) = c("tbl","data.frame")
attr(x, "t1") = "a"
y = as.data.table(x)
attr(y, "t1")
#[1] "a"       ## should be NULL
class(y)
#[1] "data.table" "data.frame"

We should assume creator of custom class provides correct data.frame method that clear any extra attributes

as.data.frame.tbl = function(x) {
  attr(x, "t1") = NULL
  class(x) = "data.frame"
  x
}
z = as.data.frame(x)
attr(z, "t1")
#NULL

So then consistency can be retained, as described in #5698

custom data.frame classes redirected to as.data.frame before as.data.…

Unmotivating the use of data.table...

Many times, one has to use haven to read data with SPSS, Stata or excel formats, which obviously produces tibbles. Fortunately, they can be transformed to data.table's and, for the moment, these transformations keep attributes, particularly variable labels. IMO, removing that information is not a big thing.

Although I use setDT instead of as.data.table...

I think that removal of attributes by as.* methods is the norm in R... users wishing to retain attributes should do so explicitly.

It's somewhat inconvenient but I think it's more the expected behavior from experienced R users.

custom data.frame classes redirected to as.data.frame before as.data.…

(textproc/R-data.table) Updated 1.16.4 to 1.18.4, Fix build against 4…

Navigation Menu

Repository navigation

as.data.table should remove extra attributes from extended data.frames #5699

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

as.data.table should remove extra attributes from extended data.frames #5699

Description

Activity

iagogv3 commented on Nov 19, 2024

MichaelChirico commented on Jan 17, 2025

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions