在下拉菜單中閃亮的顯示只有一個選擇（在幾個之間）

Question

我是Shiny的新手，對SO等類似問題的回答正在幫助我。

我想在下拉菜單上顯示動態選項，具體取決於用戶在單選按鈕上選擇的內容。但下面的代碼片段只能顯示一個亞種的選擇，一旦用戶選擇，首先＃1動物類型，然後＃2全部與亞種的選擇。

我有三個變量：＃1。動物類型（獅子vs老虎）; ＃2。整體與亞種（單選按鈕）; ＃3。亞種（如果用戶在＃2中選擇「全部」，那麼亞種應該等於「不適用」）。

供參考：

• 虎亞種= {紅，西伯利亞}

• 獅子亞種= {北非，西南非洲人，德蘭士瓦}

任何幫助理解。謝謝。

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) 
    } 

Answer 1

的問題來自於使用ifelse(test, yes, no)當是或否有不同長度的測試：

> 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" 

在你的情況 - 用3個不同長度 - 你應該使用if代替：

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") 
    } 

Answer 2

ifelse狀態的文檔：

ifelse返回一個具有與測試相同形狀的值，該測試填充了從yes或no中選擇的元素，具體取決於測試元素是TRUE還是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) 
} 

Answer 3

幾點：

（1）由於在先前的文章中提到，ifelse是這裏的罪魁禍首。 ?ifelse說

ifelse（試驗，是，否）
ifelse與相同的形狀作爲測試

這是一個在你的情況，你應該使用ifelse返回一個值按建議阻止。 （2）您可能希望在代碼中減少硬編碼，通過分離數據（可能是全局的，以便稍後您不需要更改您的R代碼來更改數據）併除去數據一些冗餘代碼：

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) 
}