dplyr：在函数中将多个变量移交给 group_by [重复]答案

【问题标题】：dplyr: Handing over multiple variables to group_by in a function [duplicate]dplyr：在函数中将多个变量移交给 group_by [重复]
【发布时间】：2019-11-26 20:28:19
【问题描述】：

我有一个dplyr::summarize 的函数。我怎样才能将多个变量交给它？

例子：

myfunction <- function(mydf, grp) {

  library(dplyr)

  grp <- enquo(grp)

  result <- mydf %>% 
    group_by(!! grp) %>% 
    summarise(sum = sum(x))

  result

}

# works
myfunction(df, grp1) 

# doesn't work
myfunction(df, c(grp1, grp2))

【问题讨论】：

标签： r function dplyr

【解决方案1】：

如果我们传递多个变量，将其作为字符串传递并使用group_by_at

myfunction <- function(mydf, grp, xvar) {  
  mydf %>%       
    group_by_at(grp) %>%
    summarise(sum = sum({{xvar}}))
 }



myfunction(mtcars, "am", mpg)
# A tibble: 2 x 2
#     am   sum
#  <dbl> <dbl>
#1     0  326.
#2     1  317.
myfunction(mtcars, c("am", "gear"), mpg)
# A tibble: 4 x 3
# Groups:   am [2]
#     am  gear   sum
#  <dbl> <dbl> <dbl>
#1     0     3 242. 
#2     0     4  84.2
#3     1     4 210. 
#4     1     5 107.

如果我们想要传递 OP 帖子中显示的组，一种方法是使用 enexpr 进行转换并评估 (!!!)

myfunction <- function(mydf, grp, xvar) {  
   grp <- as.list(rlang::enexpr(grp))
   grp <- if(length(grp) > 1) grp[-1] else grp

   mydf %>%
        group_by(!!! grp) %>%
        summarise(sum = sum({{xvar}}))

 }

myfunction(mtcars, am, mpg)
# A tibble: 2 x 2
#     am   sum
#  <dbl> <dbl>
#1     0  326.
#2     1  317.
myfunction(mtcars, c(am, gear), mpg)
# A tibble: 4 x 3
# Groups:   am [2]
#     am  gear   sum
#  <dbl> <dbl> <dbl>
#1     0     3 242. 
#2     0     4  84.2
#3     1     4 210. 
#4     1     5 107.

【讨论】：