R 在下拉菜单中仅显示一个选项（多个选项中的一个）

我对Shiny是个新手，对类似问题的回答对我很有帮助

我想在下拉菜单上显示动态选项，具体取决于用户在单选按钮上的选择。但下面的代码片段只能显示亚种的一种选择，一旦用户选择，首先#1动物类型，然后#2整个与亚种的选择

我有三个变量：#1。动物类型（狮子对老虎）#2.整体与亚种（单选按钮）#3.亚种（如果用户在#2中选择“整体”，则亚种应等于“不适用”）

供参考：

• 老虎亚种={孟加拉，西伯利亚}

• 狮子亚种={Barbary，西南非洲，特兰斯瓦尔}

感谢您的帮助。谢谢

    library(shiny)
    if (interactive()) {

    ui <- fluidPage(
     selectizeInput("VarAnimal",
               label = "Animal",
               choices = c("Tiger", "Lion"),
               selected = "Tiger"),

     radioButtons("VarWholeOrSub", 
             "Whole or Sub",
              choices = c("Whole species", "Subspecies"),
              selected = "Whole species"), 

     selectizeInput("VarSubspecies",
               label = "Subspecies",
               choices = c("Not Applicable", "Bengal", "Siberian", "Barbary", "Southwest African", "Transvaal"),
               selected = "")
    )

    server <- function(input, output, session) {
    observe({
       x <- input$VarWholeOrSub

       if (input$VarWholeOrSub == "Whole species"){
         x <- c("Not Applicable")} else{
         x <- ifelse(input$VarAnimal == "Tiger", c("Bengal", "Siberian"), c("Barbary", "Southwest African", "Transvaal"))  
    }

      updateSelectizeInput(session,
                       "VarSubspecies",
                       choices = x)

    })
    }


    shinyApp(ui, server)
    }

库（闪亮）
if（interactive（））{
ui当是或否具有不同的测试长度时，使用
ifelse（测试，是，否）
会出现问题：

> ifelse("a"=="a", c("a","b"), c("b","a"))
[1] "a"
> ifelse(rep("a"=="a",2), c("a","b"), c("b","a"))
[1] "a" "b"

在您的情况下（使用3种不同的长度），您应该使用
if
：

  if (input$VarWholeOrSub == "Whole species"){
    x <- c("Not Applicable")
    } else {
      if(input$VarAnimal == "Tiger")
        x <- c("Bengal", "Siberian")
      else
        x <- c("Barbary", "Southwest African", "Transvaal")
    }

if（输入$VarWholeOrSub==“整个物种”）{
x当“是”或“否”具有不同的测试长度时，问题来自于使用
ifelse（测试，是，否）
：

> ifelse("a"=="a", c("a","b"), c("b","a"))
[1] "a"
> ifelse(rep("a"=="a",2), c("a","b"), c("b","a"))
[1] "a" "b"

在您的情况下（使用3种不同的长度），您应该使用
if
：

  if (input$VarWholeOrSub == "Whole species"){
    x <- c("Not Applicable")
    } else {
      if(input$VarAnimal == "Tiger")
        x <- c("Bengal", "Siberian")
      else
        x <- c("Barbary", "Southwest African", "Transvaal")
    }

if（输入$VarWholeOrSub==“整个物种”）{
ifelse的文档说明：

ifelse返回一个与test形状相同的值，该值由从yes或no中选择的元素填充，具体取决于test的元素是TRUE还是FALSE

library(shiny)
if (interactive()) {

  ui <- fluidPage(
    selectizeInput("VarAnimal",
                   label = "Animal",
                   choices = c("Tiger", "Lion"),
                   selected = "Tiger"),

    radioButtons("VarWholeOrSub", 
                 "Whole or Sub",
                 choices = c("Whole species", "Subspecies"),
                 selected = "Whole species"), 

    selectizeInput("VarSubspecies",
                   label = "Subspecies",
                   choices = c("Not Applicable", "Bengal", "Siberian", "Barbary", "Southwest African", "Transvaal"),
                   selected = "")
  )

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

      if (input$VarWholeOrSub == "Whole species"){
        updateSelectizeInput(session, 'VarSubspecies', choices = c("Not Applicable"))
        } else{
          if(input$VarAnimal == "Tiger"){
            updateSelectizeInput(session, 'VarSubspecies', choices = c("Bengal", "Siberian"))
          } else if (input$VarAnimal == "Lion"){
            updateSelectizeInput(session, 'VarSubspecies', choices = c("Barbary", "Southwest African", "Transvaal"))
          }
        }
    })
  }


  shinyApp(ui, server)
} 

库（闪亮）
if（interactive（））{
ifelse的文档说明：

ifelse返回一个与test形状相同的值，该值由从yes或no中选择的元素填充，具体取决于test的元素是TRUE还是FALSE

library(shiny)
if (interactive()) {

  ui <- fluidPage(
    selectizeInput("VarAnimal",
                   label = "Animal",
                   choices = c("Tiger", "Lion"),
                   selected = "Tiger"),

    radioButtons("VarWholeOrSub", 
                 "Whole or Sub",
                 choices = c("Whole species", "Subspecies"),
                 selected = "Whole species"), 

    selectizeInput("VarSubspecies",
                   label = "Subspecies",
                   choices = c("Not Applicable", "Bengal", "Siberian", "Barbary", "Southwest African", "Transvaal"),
                   selected = "")
  )

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

      if (input$VarWholeOrSub == "Whole species"){
        updateSelectizeInput(session, 'VarSubspecies', choices = c("Not Applicable"))
        } else{
          if(input$VarAnimal == "Tiger"){
            updateSelectizeInput(session, 'VarSubspecies', choices = c("Bengal", "Siberian"))
          } else if (input$VarAnimal == "Lion"){
            updateSelectizeInput(session, 'VarSubspecies', choices = c("Barbary", "Southwest African", "Transvaal"))
          }
        }
    })
  }


  shinyApp(ui, server)
} 

库（闪亮）
if（interactive（））{
ui几点：

（1） 如前几篇文章所述，
ifelse
是罪魁祸首。
？如果其他
说

ifelse（测试，是，否）

ifelse返回一个与test形状相同的值

在您的情况下，您应该按照建议使用if-else块

（2） 您可能希望代码中的硬编码更少，方法是分离数据（可能是全局的，以便以后不需要更改R代码来更改数据）并去掉一些冗余代码：

df <- data.frame(Animals = c("Tiger", "Lion"), 
                 WholeSpecies=rep("Not Applicable", 2),
                 SubSpecies=c("Bengal, Siberian", "Barbary, Southwest African, Transvaal"), 
                 stringsAsFactors = FALSE)
head(df)
#  Animals   WholeSpecies                            SubSpecies
#1   Tiger Not Applicable                      Bengal, Siberian
#2    Lion Not Applicable Barbary, Southwest African, Transvaal

library(shiny)
if (interactive()) {

  ui <- fluidPage(
    selectizeInput("VarAnimal",
                   label = "Animal",
                   choices = df$Animals,
                   selected = df$Animals[1]),

    radioButtons("VarWholeOrSub", 
                 "Whole or Sub",
                 choices = c("Whole species", "Subspecies"),
                 selected = "Whole species"), 

    selectizeInput("VarSubspecies",
                   label = "Subspecies",
                   choices = c(unique(df$WholeSpecies), unlist(strsplit(unique(df$SubSpecies), split=','))),
                   selected = "")
  )

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

      x <- df[df$Animals==input$VarAnimal,]$WholeSpecies

      if (input$VarWholeOrSub == "Subspecies"){
        x <- unlist(strsplit(df[df$Animals==input$VarAnimal,]$SubSpecies, split=','))
      }

      updateSelectizeInput(session,
                           "VarSubspecies",
                           choices = x)

    })
  }

  shinyApp(ui, server)
}

df两点：

（1） 如前几篇文章所述，
ifelse
是罪魁祸首。
？如果其他
说

ifelse（测试，是，否）

ifelse返回一个与test形状相同的值

在您的情况下，您应该按照建议使用if-else块

（2） 您可能希望代码中的硬编码更少，方法是分离数据（可能是全局的，以便以后不需要更改R代码来更改数据）并去掉一些冗余代码：

df <- data.frame(Animals = c("Tiger", "Lion"), 
                 WholeSpecies=rep("Not Applicable", 2),
                 SubSpecies=c("Bengal, Siberian", "Barbary, Southwest African, Transvaal"), 
                 stringsAsFactors = FALSE)
head(df)
#  Animals   WholeSpecies                            SubSpecies
#1   Tiger Not Applicable                      Bengal, Siberian
#2    Lion Not Applicable Barbary, Southwest African, Transvaal

library(shiny)
if (interactive()) {

  ui <- fluidPage(
    selectizeInput("VarAnimal",
                   label = "Animal",
                   choices = df$Animals,
                   selected = df$Animals[1]),

    radioButtons("VarWholeOrSub", 
                 "Whole or Sub",
                 choices = c("Whole species", "Subspecies"),
                 selected = "Whole species"), 

    selectizeInput("VarSubspecies",
                   label = "Subspecies",
                   choices = c(unique(df$WholeSpecies), unlist(strsplit(unique(df$SubSpecies), split=','))),
                   selected = "")
  )

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

      x <- df[df$Animals==input$VarAnimal,]$WholeSpecies

      if (input$VarWholeOrSub == "Subspecies"){
        x <- unlist(strsplit(df[df$Animals==input$VarAnimal,]$SubSpecies, split=','))
      }

      updateSelectizeInput(session,
                           "VarSubspecies",
                           choices = x)

    })
  }

  shinyApp(ui, server)
}

df非常感谢！很抱歉，你的答案在HubertL之后出现了一点……否则，我会把你的答案作为投票结果……没问题。更重要的是要知道问题的原因/原因。很高兴你能够继续解决你的问题。非常感谢！很抱歉，你的答案在HubertL之后出现了一点……否则，我会投票给你答案是urs…不是问题。更重要的是要知道问题的原因/原因。很高兴你能够继续解决问题。