r - 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_* 我想打开或关闭无，一列或多列作为分组依据。我没有看到，如何在 group_by(string) 中构造字符串

Answer 1

您可以创建一个 rlang::expr 对象的向量，然后将其子集化为您想要使用的值，并使用 将其扩展到 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)
}