问题描述
以下几行突出显示了该问题。属性在许多情况下会被转移，但不是在最后一种情况下，这是一个常见的“总结”用例。非常感谢任何帮助！
suppressWarnings(suppresspackageStartupMessages(library(dplyr)))
obj <- c(12,13,51)
attributes(obj)<- list(cv = c(3,4,2))
print(obj)
#> [1] 12 13 51
#> attr(,"cv")
#> [1] 3 4 2
## 'obj' has an attribute
print(attributes(obj))
#> $cv
#> [1] 3 4 2
tbl <- tibble::tibble(col = obj)
print(tbl$col)
#> [1] 12 13 51
#> attr(,"cv")
#> [1] 3 4 2
## attributes are retained by the col obj was assigned to
print(attributes(tbl$col))
#> $cv
#> [1] 3 4 2
foo <- function(x){
# to be called within 'summarise()'
o <- sum(x)
attributes(o)<- list(cvv = o*2)
return(o)
}
# produces values with attributes
print(foo(7))
#> [1] 7
#> attr(,"cvv")
#> [1] 14
tbl2 <- tbl %>%
summarise(z = foo(col))
# with one single row,attributes are transferred to tbl2
print(attributes(tbl2$z))
#> $cvv
#> [1] 152
tbl2 <- tbl %>%
group_by(col) %>%
summarise(z = foo(col),.groups = "keep")
# with more rows,attributes are NO longer present in tbl2
print(attributes(tbl2$z))
#> NULL
由 reprex package (v0.3.0) 于 2021 年 4 月 25 日创建
解决方法
谢谢，是的 Akrun 你是对的，列表包装实际上保留了属性！
要完成答案并获得所需的结果（具有属性的非列表列），据我所知，需要一个相当复杂的过程（请参阅代码）。
是否有可能在不中断“管道”流程的情况下实现相同的结果？
suppressWarnings(suppressPackageStartupMessages(library(dplyr)))
suppressWarnings(suppressPackageStartupMessages(library(purrr)))
obj <- c(12,13,51)
attributes(obj)<- list(cv = c(3,4,2))
tbl <- tibble::tibble(col = obj)
print(attributes(tbl$col))
#> $cv
#> [1] 3 4 2
foo <- function(x){
# to be called within 'summarise()'
o <- sum(x)
attributes(o)<- list(cvv = o*2)
return(o)
}
tbl2 <- tbl %>%
group_by(col) %>%
summarise(z = list(foo(col)),.groups = "keep")
atts <- map_df(tbl2$z,attributes)
tbl2 <- tbl2 %>%
mutate(z = unlist(z))
attributes(tbl2$z)<- atts
# now attributes are present in tbl2!!! but the flow is somewhat twisted!
print(attributes(tbl2$z))
#> $cvv
#> [1] 24 26 102
由 reprex package (v0.3.0) 于 2021 年 4 月 26 日创建