如何创建动态 group_by 参数

Question

我想按组汇总数据框。要分组的列在不同的编译中动态定义。这里有一个例子。

gender = c(rep(1, 50), rep(2, 50))
weight = round(rnorm(100, 60, 5), 0)
age = floor(runif(100, min=18, max=30))
my_df <- data.frame(gender, age, weight)

result <- function(
  df = my_df,
  group_by_gender = TRUE,
  group_by_weight = TRUE,
  group_by_age = TRUE
){
  the_result <- df %>%
    group_by(
      gender, #if(group_by_gender, gender, NULL),
      weight, #if(group_by_weight, weight, NULL),
      age #if(group_by_age, age, NULL)
    ) %>%
    summarize(
      count = n()
    )
  return(the_result)
}

根据 group_by_* 我想打开或关闭一个或多个列进行分组。我没有看到，如何在 group_by(string) 中构造字符串

Answer 1

您可以创建rlang::expr 对象的向量，然后将其子集为您要使用的值，然后将其扩展为带有!!! 的group_by。例如

result <- function(
  df = my_df,
  group_by_gender = TRUE,
  group_by_weight = TRUE,
  group_by_age = TRUE
){
  gcols <- rlang::exprs(gender, weight, age)
  gkeep <- c(group_by_gender, group_by_weight, group_by_age)
  the_result <- df %>%
    group_by(!!!gcols[gkeep]) %>%
    summarize(
      count = n()
    )
  return(the_result)
}

Answer 2

您可以在group_by 函数中调用.dots 参数：

result <- function(df = my_df, group_by_gender = TRUE, 
                   group_by_weight = TRUE, group_by_age = TRUE){
  nms <- c("gender","weight", "age")
  bool <- c(group_by_gender, group_by_weight, group_by_age)
  
  the_result <- df %>%
    group_by(.dots = nms[bool]) %>%
    summarize(count = n(), .groups = "keep")
  return(the_result)
}