我在R中使用data.table
来处理包含元数据的数据。这些元数据存储在“comment”属性中,用于提供数据的时间戳。但是,在对数据进行子集操作时,元数据会被删除。例如:
library(data.table)
dt <- data.table(x = c(1:5), y = c(6:10))
setattr(dt, 'comment', 'december 10, 2015')
comment(dt) # The metadata is present here...
# [1] "december 10, 2015"
comment(dt[x < 3]) # ...but not retained here
# NULL
data.frame
与之相反,不会表现出同样的行为。例如,
df <- data.frame(x = c(1:5), y = c(6:10))
comment(df) <- "december 2015"
comment(df) # Metadata again is present
# [1] "december 2015"
comment(df[df$x < 3, ]) # Metadata is retained
# [1] "december 2015"
请问是否有办法让data.table
在这些子集中保留元数据?