如何在闪亮中将文本传递给 summarise（）

问：

我正在构建一个 shinyapp。我尝试将用户选择为 char 的函数保存到 a 中，然后用于生成类似“n = n（）， sum = sum（value）， mean = mean（value）” 或更短的东西，最后传递给 summarise（）
我尝试了 和 ，都失败了。data.frame()paste()enquote()eval(parse())

library(shiny)
library(shinyjs)
library(tidyverse)

ui <- fluidPage(
  useShinyjs(),
  fluidRow(
    column(width = 3,
      wellPanel(
        selectInput("data_groupby", label = "group_by", choices = c(Choose = "", "group", "sameple", "var"), selected = c("group", "var"), multiple = TRUE),
        actionButton("data_groupby_ok", "click here to group_by"),
        selectInput("data_summarise_fun", "Function", choices = c(Choose = "", "n", "sum", "mean")),
        actionButton("data_summarise_add", "Summarise"),
        h4("paras to be passed to summarise():"),
        verbatimTextOutput("summarise_paras")
      )
    ),
    column(width = 3,
      h4("data:"),
      verbatimTextOutput("data")
    ),
    column(width = 3,
      h4("data_summarised:"),
      verbatimTextOutput("data_summarised")
    ),
    column(width = 3,
      h4("data_desired (if add 3 functions):"),
      verbatimTextOutput("data_desired")
    )
  )
)

server <- function(input, output, session) {

  aggr <- reactiveValues(
    data = NULL,
    summarise_paras = data.frame(column = character()),
    data_grouped = NULL,
    data_summarised = NULL,
    data_desired = NULL
  )

  set.seed(50)
  aggr$data <- data.frame(
    group = rep(LETTERS[1:3], each = 6),
    sample = rep(c(paste0("A_", 1:3), paste0("B_", 1:3), paste0("C_", 1:3)), each = 2),
    var = rep(c("height", "weight"), times = 9),
    value = runif(18, min = 0, max = 1)
  )

  aggr$data_desired <- data.frame(
    group = rep(LETTERS[1:3], each = 6),
    sample = rep(c(paste0("A_", 1:3), paste0("B_", 1:3), paste0("C_", 1:3)), each = 2),
    var = rep(c("height", "weight"), times = 9),
    value = runif(18, min = 0, max = 1)
  ) %>%
    group_by(group, var) %>% summarise(n = n(), sum = sum(value), mean = mean(value))

  observeEvent(input$data_groupby_ok, {
    groupby <- input$data_groupby
    aggr$data_grouped <- aggr$data %>% group_by(across(all_of(groupby)))
    disable("data_groupby")
  })

  observe({
    toggleState("data_summarise_add", nchar(input$data_summarise_fun) >0)
  })

  observeEvent(input$data_summarise_add, {

    tryCatch({
      fun <- input$data_summarise_fun

      if (fun == "n") {
        para <- "n = n()"
      } else if (fun == "sum") {
        para <- "sum = sum(value)"
      } else if (fun == "mean") {
        para <- "mean = mean(value)"
      }
      aggr$summarise_paras <- aggr$summarise_paras %>%
                              filter(column != para) %>%
                              bind_rows(data.frame(column = para))
      paras <- paste(aggr$summarise_paras$column, collapse = ",")
      aggr$data_summarised <- aggr$data_grouped %>% summarise(enquote(paras))

      reset("data_summarise_fun")
    }, error = function(e) {
      showNotification(paste(e$message), type = "error", duration = 5)
    })
  })

  output$data <- renderPrint({print(aggr$data)})
  output$summarise_paras <- renderPrint({print(aggr$summarise_paras)})
  output$data_summarised <- renderPrint({print(aggr$data_summarised)})
  output$data_desired <- renderPrint({print(aggr$data_desired)})
}

shinyApp(ui = ui, server = server)

我想要的输出是 ，它打印在我闪亮的示例中aggr$data_desired