r - 使用 "{{"运算符通过环境变量隧道数据变量

Question

遵循 https://www.tidyverse.org/blog/2020/02/glue-strings-and-tidy-eval/ 中的示例

如何将变量传递给这个函数？

library(tidyverse)
#> Warning: package 'tidyverse' was built under R version 3.6.2
#> Warning: package 'tidyr' was built under R version 3.6.2

mean_by <- function(data, by, var, prefix = "avg") {
  data %>%
    group_by({{ by }}) %>%
    summarise("{prefix}_{{ var }}" := mean({{ var }}, na.rm = TRUE))
}

mean_by(mtcars, by = cyl, var = mpg, prefix = "avg")
#> # A tibble: 3 x 2
#>     cyl avg_mpg
#>   <dbl>   <dbl>
#> 1     4    26.7
#> 2     6    19.7
#> 3     8    15.1

# Variables to pass into function
params <-  setdiff(colnames(mtcars) ,"mpg") 

# How do you pass a variables into this function? 
purrr::map(params, mean_by(mtcars, by = .x, var = mpg, prefix = "avg"))
#> Error: Column `.x` is unknown

^{由 reprex package 创建于 2020-02-19 (v0.3.0)}

Answer 1

对列名使用.data代词:

purrr::map(params, ~ mean_by(mtcars, by = .data[[.x]], var = mpg, prefix = "avg"))