為什么從總和切換到計算唯一出現次數時dplyr中的group_by()不起作用？

下面的 MWE 代碼適用于對資料框值求和，用戶可以在底部呈現的“對資料表列求和：”部分的單選按鈕中選擇要分組的周期型別。此分組summed_data()在本server節下面的物件中執行。

但是，我也在嘗試計算 Period_2 == 1 的出現次數。當我注釋掉summed_data()下面當前未注釋的部分，并取消注釋當前已注釋掉的summed_data()以執行唯一行計數，并嘗試運行代碼時，它失敗了。但是，如果我在 R 控制臺中運行這個獨特的行計數函式，如下所示，它可以正常作業并提供所需的結果（手動更改該部分中的“Period...” group_by(...)）！

   data <- data.frame(
      ID = c(115,115,111,88,120,16),
      Period_1 = c("2020-01", "2020-02", "2020-03", "2020-01", "2020-02", "2020-03"),
      Period_2 = c(1, 2, 3, 1, 1, 4),
      ColA = c(1000.01, 20, 30, 40, 50, 60),
      ColB = c(15.06, 25, 35, 45, 55, 65)
    )
    
    filter(data, Period_2 == "1") %>%
    group_by(Period_1) %>%
    summarise(count = length(unique(ID)))

 Period_1 count
  <chr>    <int>
1 2020-01      2
2 2020-02      1

所以，對我來說，問題似乎出在下面的 dplyr 代碼中group_by(!!sym(input$grouping))。有沒有人有解決這個問題的建議？

MWE代碼：

library(dplyr)
library(DT)
library(shiny)
library(shinyWidgets)
library(tidyverse)

ui <-
  fluidPage(
    fluidRow(
      column(width = 8,
          h3("Data table:"),
          tableOutput("data"),
          h3("Sum the data table columns:"),
          radioButtons(
            inputId = "grouping",
            label = NULL,
            choiceNames = c("By period 1", "By period 2"),
            choiceValues = c("Period_1", "Period_2"),
            selected = "Period_1",
            inline = TRUE
          ),
          DT::dataTableOutput("sums")
      )
    )
  )

server <- function(input, output, session) {
  data <- reactive({
    data.frame(
      ID = c(115,115,111,88,120,16),
      Period_1 = c("2020-01", "2020-02", "2020-03", "2020-01", "2020-02", "2020-03"),
      Period_2 = c(1, 2, 3, 1, 1, 4),
      ColA = c(1000.01, 20, 30, 40, 50, 60),
      ColB = c(15.06, 25, 35, 45, 55, 65)
    )
  })
  
  colNames <- reactive({c(input$grouping, "Col A", "Col B") })
  
  # summed_data <- reactive({
  #   filter(data(), Period_2 == "1") %>%
  #     group_by(!!sym(input$grouping)) %>%
  #     summarise(count = length(unique(ID)))
  # })
  
  summed_data <- reactive({
    data() %>%
      group_by(!!sym(input$grouping)) %>%
      select("ColA","ColB") %>%
      summarise(across(everything(), sum))
  })
  
  output$data <- renderTable(data())

  output$sums <- renderDT({
    summed_data() %>% 
      datatable(
        rownames = FALSE,
        colnames=colNames() # < add colNames()
        )
  })
  
}

shinyApp(ui, server)

uj5u.com熱心網友回復：

問題colNames()在于您定義并添加到對datatable. 我把這些行注釋掉了，它起作用了。你的問題沒有出現，sum data.frame因為這里colnames實際上存在于 中data.frame，而length(unique)) data.frame.

library(dplyr)
library(DT)
library(shiny)
library(shinyWidgets)
library(tidyverse)

ui <-
  fluidPage(
    fluidRow(
      column(width = 8,
             h3("Data table:"),
             tableOutput("data"),
             h3("Sum the data table columns:"),
             
             radioButtons(
               inputId = "grouping",
               label = NULL,
               choiceNames = c("By period 1", "By period 2"),
               choiceValues = c("Period_1", "Period_2"),
               selected = "Period_1",
               inline = TRUE
             ),
             DT::dataTableOutput("sums")
      )
    )
  )

server <- function(input, output, session) {
  mydat <- reactive({
    data.frame(
      ID = c(115,115,111,88,120,16),
      Period_1 = c("2020-01", "2020-02", "2020-03", "2020-01", "2020-02", "2020-03"),
      Period_2 = c(1, 2, 3, 1, 1, 4),
      ColA = c(1000.01, 20, 30, 40, 50, 60),
      ColB = c(15.06, 25, 35, 45, 55, 65)
    )
  })
  
  # colNames <- reactive({c(input$grouping, "Col A", "Col B") })
  
  summed_data <- reactive({
    print(input$grouping)
    mydat() %>%
      dplyr::filter(Period_2 == 1) %>%
      dplyr::group_by(!!sym(input$grouping)) %>% 
      dplyr::summarise(count = length(unique(ID)))
  })
  
  # summed_data <- reactive({
  #   print(input$grouping)
  #   data() %>%
  #     group_by(across(all_of(input$grouping))) %>%
  #     select("ColA","ColB") %>%
  #     summarise(across(everything(), sum))
  # })
  
  output$data <- renderTable(mydat())
  
  output$sums <- renderDT({
    summed_data() %>% 
      datatable(
        rownames = FALSE,
        # colnames=colNames() # < add colNames()
      )
  })
  
}

shinyApp(ui, server)

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