用户指定的data.table属性将被删除

Question

我有一个函数返回一个data.table附加了各种有用的用户定义属性.但是,我注意到,当操纵data.table时,属性会消失.

library(data.table)
my_dt <- data.table(col1 = rnorm(20), col2 = letters[1:20])

# store some user attribute
attr(my_dt, 'title') <- 'This is my data.table'
# now it's there
attributes(my_dt)
# but here it's gone
attributes(my_dt[order(col1)]) 

有没有办法让data.table'persist'的属性适用于上述情况(除了将它们存储在一个单独的对象中)？

似乎属性确实存在于常规 data.frames

my_df <- data.frame(col1 = rnorm(20), col2 = letters[1:20])

# store some user attribute
attr(my_df, 'title') <- 'This is my data.frame'
# there it is
attributes(my_df) 
# still there
attributes(my_df[order(my_df$col1), ]) 

Answer 1

当 Matt 使子集并行时，功能已添加到 1.12.0。所以属性现在被保留了。

library(data.table)
my_dt <- data.table(col1 = rnorm(20), col2 = letters[1:20])

attr(my_dt, 'title') <- 'This is my data.table'
attr(my_dt, 'title')
#[1] "This is my data.table"
attr(my_dt[order(col1)], 'title')
#[1] "This is my data.table"