在 dplyr 包中以链接方式添加属性 [英] Adding attributes in chaining way in dplyr package

问题描述

有没有办法使用 dplyr 包中的链接序列代码运算符 %>% 添加属性?

Is there any way to add an attribute using chaining sequence code operator %>% from dplyr package?

> library(dplyr)
> iris %>%
+   attr( "date") = Sys.Date()
Error in iris %>% attr("date") = Sys.Date() : 
  could not find function "%>%<-"
> 

感谢回复.

推荐答案

你也可以从data.table"中考虑setattr:

You can also consider setattr from "data.table":

library(dplyr)
library(data.table)
names(attributes(iris))
# [1] "names"     "row.names" "class" 

iris %>% setattr(., "date", Sys.Date())
names(attributes(iris))
# [1] "names"     "row.names" "class"     "date" 
attributes(I2)$date
# [1] "2014-09-04"

当然，这样的事情实际上不需要链接.你可以这样做:

Of course, no chaining is actually required for something like this. You could just do:

setattr(iris, "date", Sys.Date())

这允许您在不复制相关对象的情况下设置属性:

This allows you to set attributes without copying the objects in question:

> v1 <- 1:4
> v2 <- 1:4
> tracemem(v1)
[1] "<0x0000000011cffa38>"
> attr(v1, "foo") <- "bar"
tracemem[0x0000000011cffa38 -> 0x0000000011d740f8]: 
> tracemem(v2)
[1] "<0x0000000011db2da0>"
> setattr(v2, "foo", "bar")
> attributes(v2)
$foo
[1] "bar"

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