下面的例子来自https://www.tidyverse.org/blog/2020/02/glue-strings-and-tidy-eval/ https://www.tidyverse.org/blog/2020/02/glue-strings-and-tidy-eval/
如何将变量传递到这个函数中?
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
Created on 2020-02-19 by the reprex package https://reprex.tidyverse.org (v0.3.0)
Use the .data
代词与列名:
purrr::map(params, ~ mean_by(mtcars, by = .data[[.x]], var = mpg, prefix = "avg"))
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