group_by dplyr函数闪亮

Question

使用Shiny时,我无法在dplyr工作中获得group_by.似乎dplyr无法将Shiny的输入$ var识别为表中的有效字段.

在这个例子中,我希望ui.R中的"level"输入决定分组的内容.

在ui.RI有:

library(shiny)
shinyUI(fluidPage(
titlePanel("Orders"),
sidebarLayout(
sidebarPanel(
  selectInput("Region_Input", label = h5("Choose a Region"), 
              choices = list("A", "B")),
  radioButtons("level", "What level do you want to see:",
                     list("item", "category"))

),
mainPanel(
  verbatimTextOutput("Level_Select"),
  tableOutput(outputId="table")

))))

在server.RI中有:

library(shiny)  
library(dplyr)

OrderItems <- data.frame(Region =      c('A','A','A','A','A','A','B','B','B','B','B','B','B'),
                     item = c('Item A','Item B','Item C','Item D','Item E',
                              'Item A','Item B','Item C','Item D','Item E',
                              'Item A','Item B','Item C'),
                     category = c('Cat 1','Cat 1','Cat 1','Cat 2','Cat 2',
                                  'Cat 1','Cat 1','Cat 1','Cat 2','Cat 2',
                                  'Cat 1','Cat 1','Cat 1'))
shinyServer(
function(input, output) {

output$table <- renderTable({
  OrderItems %>%
    group_by(input$level) %>%
    summarize(count = n()) %>%
    arrange(desc(count))    
})
})

当"级别"输入为"类别"时,我期望的输出是:

   category count
1   Cat 1   9
2   Cat 2   4

但是,我最终获得的是:

    input$level count
1   category           13

如何解决这个问题的任何想法将不胜感激!

Answer 1

每@ joran的评论,这应该是在更换简单group_by(input$level)用group_by_(input$level),但它很难不重复的例子说.如果您进行一些更改并利用mtcars数据,可以重现以下内容以查看其工作原理:

server.R

library(shiny)  
library(dplyr)

shinyServer(
  function(input, output) {

    output$table <- renderTable({
      mtcars %>%
        group_by_(input$level) %>%
        summarize(count = n()) %>%
        arrange(desc(count))    
    })
  })

ui.R

library(shiny)
shinyUI(fluidPage(
  titlePanel("Orders"),
  sidebarLayout(
    sidebarPanel(
      selectInput("Region_Input", label = h5("Choose a Region"), 
                  choices = list("A", "B")),
      radioButtons("level", "What level do you want to see:",
                   list("cyl", "am"))

    ),
    mainPanel(
      verbatimTextOutput("Level_Select"),
      tableOutput(outputId="table")

    ))))