R Data.table使用向量循环创建动态列名

我想在data.table中复制dplyr的行为，以便通过group_by和reframe扩展行.我可以通过自己设置列名来完成，但如果我设置动态列名(即，基于外部向量).示例如下:

library(data.table)
library(dplyr)

iris <- as.data.table(iris)

# Dplyr
varname <- c("new_var")
var_levels <- c("level1", "level2")
iris %>% 
  group_by(pick(everything())) %>% 
  reframe({{varname}} := var_levels) 
#> # A tibble: 298 × 6
#>    Sepal.Length Sepal.Width Petal.Length Petal.Width Species new_var
#>           <dbl>       <dbl>        <dbl>       <dbl> <fct>   <chr>  
#>  1          4.3         3            1.1         0.1 setosa  level1 
#>  2          4.3         3            1.1         0.1 setosa  level2 
#>  3          4.4         2.9          1.4         0.2 setosa  level1 
#>  4          4.4         2.9          1.4         0.2 setosa  level2 
#>  5          4.4         3            1.3         0.2 setosa  level1 
#>  6          4.4         3            1.3         0.2 setosa  level2 
#>  7          4.4         3.2          1.3         0.2 setosa  level1 
#>  8          4.4         3.2          1.3         0.2 setosa  level2 
#>  9          4.5         2.3          1.3         0.3 setosa  level1 
#> 10          4.5         2.3          1.3         0.3 setosa  level2 
#> # ℹ 288 more rows


# Data.table:
iris[, .(new_var = var_levels) , keyby = names(iris)]
#>      Sepal.Length Sepal.Width Petal.Length Petal.Width   Species new_var
#>   1:          4.3         3.0          1.1         0.1    setosa  level1
#>   2:          4.3         3.0          1.1         0.1    setosa  level2
#>   3:          4.4         2.9          1.4         0.2    setosa  level1
#>   4:          4.4         2.9          1.4         0.2    setosa  level2
#>   5:          4.4         3.0          1.3         0.2    setosa  level1
#>  ---                                                                    
#> 294:          7.7         3.0          6.1         2.3 virginica  level2
#> 295:          7.7         3.8          6.7         2.2 virginica  level1
#> 296:          7.7         3.8          6.7         2.2 virginica  level2
#> 297:          7.9         3.8          6.4         2.0 virginica  level1
#> 298:          7.9         3.8          6.4         2.0 virginica  level2


# Dynamic data.table?
iris[, (varname) := var_levels, keyby= names(iris)] 
#> Error in `[.data.table`(iris, , `:=`((varname), var_levels), keyby = names(iris)): Supplied 2 items to be assigned to group 1 of size 1 in column 'new_var'. The RHS length must either be 1 (single values are ok) or match the LHS length exactly. If you wish to 'recycle' the RHS please use rep() explicitly to make this intent clear to readers of your code.

^{创建于2023-11-22，共reprex v2.0.2个}

我能想到的唯一解决办法是:

iris[, .(varname = var_levels) , keyby = names(iris)]
iris <- iris %>% rename({{varname}} := varname)