r - 只有一个项目的分组选择输入

Question

我想按照此处的说明对我的 selectInput 数据进行分组:https://shiny.rstudio.com/gallery/option-groups-for-selectize-input.html .除了组中只有一个项目的情况外，一切正常。

这是一个示例(第一个正确的 selectInput 和奇怪的第二个):

library(shiny)

ui <- fluidPage(
    selectInput("country", "Select country", list(
        "Europe" = c("Germany", "Spain"),
        "North America" = c("Canada", "United States" = "USA")
    )),

    selectInput("country", "Select country", list(
        "Europe" = c("Germany", "Spain"),
        "North America" = c("Canada")
    ))
)

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

shinyApp(ui = ui, server = server) 

效果:

你知道怎么处理吗？

Answer 1

我不知道为什么会这样，但这对我来说是这样的

library(shiny)

ui <- fluidPage(
  selectInput("country", "Select country", list(
    "Europe" = c("Germany", "Spain"),
    "North America" = c("Canada", "United States" = "USA")
  )),

  selectInput("country", "Select country", list(
    "Europe" = c("Germany", "Spain"),
    "North America" = c("Canada", "")
  ))
)

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

shinyApp(ui = ui, server = server)

代码的唯一区别是我在此处添加了"" "North America"= c("Canada", "")。这给了我