使用 dplyr 进行问题编程——列绝对是一个被选取为公式的向量

Question

我正在编写一个函数来使用 highcharter 重现几个图表，这些图表都将具有类似的格式（和其他内容）。如果名称发生更改，或者如果我想做一些不同的事情并且我正在接受这些参数，我希望能够选择数据集的不同列{{ }}。但是后来我收到了这个奇怪的错误：

Error: Problem with `mutate()` input `x`.
x Input `x` must be a vector, not a `formula` object.
i Input `x` is `~Year`.

这是我的（最小可重现）代码：

library(dplyr)
library(highcharter)

plot_high_chart <- function(.data,
                            chart_type = "column",
                            x_value = Year,
                            y_value = total,
                            group_value = service) {
  .data %>% 
  hchart(chart_type, hcaes(x = {{x_value}}, y = {{y_value}}, group = {{group_value}}))
}

data %>% plot_high_chart()

这是dput数据的结果：

structure(list(Year = c(2016, 2017, 2017, 2018, 2018, 2018), 
    service = structure(c(10L, 3L, 9L, 5L, 7L, 9L), .Label = c("Defense Logistics Agency", 
    "Chemical and Biological Defense Program", "Defense Information Systems Agency", 
    "United States Special Operations Command", "Office of the Secretary Of Defense", 
    "Missile Defense Agency", "Defense Advanced Research Projects Agency", 
    "Navy", "Army", "Air Force"), class = "factor"), total = c(9.435, 
    0, 10.442, 9.969, 73.759, 8.855)), row.names = c(NA, -6L), groups = structure(list(
    Year = c(2016, 2017, 2018), .rows = structure(list(1L, 2:3, 
        4:6), ptype = integer(0), class = c("vctrs_list_of", 
    "vctrs_vctr", "list"))), row.names = c(NA, 3L), class = c("tbl_df", 
"tbl", "data.frame"), .drop = TRUE), class = c("grouped_df", 
"tbl_df", "tbl", "data.frame"))

Answer 1

{{a}}是 的简写!!enquo(a)，它捕获提供给的表达式a以及应评估该表达式的上下文。在您的情况下，上下文是数据框，它已经提供给函数。rlang因此，这里使用的更好的动词是ensym(a)，它捕获提供给的符号名称a：

plot_high_chart <- function(.data,
                            chart_type = "column",
                            x_value = "Year",             # <-- Note: strings
                            y_value = "total",            
                            group_value = "service") {
  .data %>%
      hchart(chart_type, hcaes(x = !!rlang::ensym(x_value),    # <- ensym instead of {{
                               y = !!rlang::ensym(y_value),
                               group = !!rlang::ensym(group_value)))
}

作为奖励，该函数现在可以使用符号和字符串：

data %>%
   plot_high_chart(x_value= "Year", y_value= "total", group_value= "service")    # Works
data %>% 
   plot_high_chart(x_value= Year, y_value= total, group_value= service)     # Also Works