闪亮的错误：尝试从 selectInput 中选择少于一个元素答案

【问题标题】：Shiny error: attempt to select less than one element from selectInput闪亮的错误：尝试从 selectInput 中选择少于一个元素
【发布时间】：2016-01-24 22:07:04
【问题描述】：

如何在 Shiny 的 selectInput 调用中添加要从中选择的类变量，以从 ggplot 生成条形图？在我的数据集总数中，我想选择 Class 变量以生成不同的 ggplot 条形图。我收到错误：“尝试选择少于一个元素”。

    totals<-data.frame(Class=c("A","A","A","B","B","B","c","C","D","D","D","D"),
               Type=c("Type1","Type2","Type3","Type1","Type2","Type3","Type1",
                      "Type2","Type1","Type2","Type3","Type4"),
               Acres=c(45,543,434,434,434,455,683,345,567,77,52,86))

server.r 代码如下：

    library(shiny)
    library(ggplot2)

    shinyServer(function(input, output, session) {

    output$acresPlot <- reactivePlot(function() {

    acresData <- data.frame(acres = totals$Acres, var = factor(totals[[input$variable]]))

    p <- ggplot(acresData, aes(var, acres)) + 
    geom_bar(stat="identity") 
    print(p)
    })
    })

ui.r 代码如下：

    shinyUI(pageWithSidebar(
    headerPanel("My types by class"),

    sidebarPanel(
    selectInput("Class", "Class:",
            c("A" = "A", 
                 "B" = "B", 
                 "C" = "C",
                 "D"="D"))),
    mainPanel(
    plotOutput("acresPlot")
    )
     ))

【问题讨论】：

标签： r ggplot2 shiny

【解决方案1】：

我不完全确定你想要什么，但如果你只想一次选择一门课，你可以这样做：

library(shiny)
library(ggplot2)

totals<-data.frame(Class=c("A","A","A","B","B","B","c","C","D","D","D","D"),
                   Type=c("Type1","Type2","Type3","Type1","Type2","Type3","Type1",
                          "Type2","Type1","Type2","Type3","Type4"),
                   Acres=c(45,543,434,434,434,455,683,345,567,77,52,86))

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

  output$acresPlot <- renderPlot(function() {
    inds <- totals$Class == input$Class
    acresData <- data.frame(acres = totals$Acres[inds], var = totals$Class[inds])

    p <- ggplot(acresData, aes(var, acres)) + 
      geom_bar(stat="identity") 
    print(p)
  })

  output$acresPlot2 <- renderPlot(function() {
    inds <- totals$Class == input$Class
    acresData <- data.frame(acres = totals$Acres, var = totals$Class, col=inds)

    p <- ggplot(acresData, aes(var, acres, fill =col)) + 
      geom_bar(stat="identity") 
    print(p)
  })
})

ui <- shinyUI(pageWithSidebar(
  headerPanel("My types by class"),

  sidebarPanel(
    selectInput("Class", "Class:",
                c("A" = "A", 
                  "B" = "B", 
                  "C" = "C",
                  "D"="D"))),
  mainPanel(
    plotOutput("acresPlot"),
    plotOutput("acresPlot2")
  )
))

shinyApp(ui=ui,server = server)

acresPlot 显示所选栏，acresPlot2 显示所选栏以及所有其他栏。

【讨论】：

谢谢@Oscar。指定 inds[] 对象效果很好。