当 multiple 为真时，如何限制用户可以 select 使用 selectInput in R shiny 的选项数量？

Question

我有一个 Shiny 应用程序，我希望用户能够 select 多个选项——但仅限于一定的限制。我找不到限制人数的方法。

下面是一个简单的、可重现的例子。在其中，我是用户只能 select 第一个问题最多 2/4 个选项，第二个最多 3/4 个选项，第三个问题他们想要多少个选项（否问题 3 需要修改）。

library(shiny)

ui <- fluidPage(
  
  
  sidebarLayout(
    sidebarPanel(                     selectInput("q1", label = "Choose up to 2.", choices = c(" ", "option 1", "option 2", "option 3", "option 4"), multiple = TRUE),
                                      selectInput("q2", label = "Choose up to 3.", choices = c(" ", "option 1", "option 2", "option 3", "option 4"), multiple = TRUE),
                                      selectInput("q3", label = "Choose as many as you want.", choices = c(" ", "option 1", "option 2", "option 3", "option 4"), multiple = TRUE)),
    mainPanel(
  
    )
  )
)

server <- function(input, output) {
  
  
}

# Run the application 
shinyApp(ui = ui, server = server)

Answer 1

您可以使用 selectizeInput 代替 selectInput 并使用 options 参数使用 maxItems.

设置允许的最大项目数

library(shiny)

ui <- fluidPage(sidebarLayout(
  sidebarPanel(
    selectizeInput(
      "q1",
      label = "Choose up to 2.",
      choices = c(" ", "option 1", "option 2", "option 3", "option 4"),
      multiple = TRUE,
      options = list(maxItems = 2)
    ),
    selectizeInput(
      "q2",
      label = "Choose up to 3.",
      choices = c(" ", "option 1", "option 2", "option 3", "option 4"),
      multiple = TRUE,
      options = list(maxItems = 3)
    ),
    selectInput(
      "q3",
      label = "Choose as many as you want.",
      choices = c(" ", "option 1", "option 2", "option 3", "option 4"),
      multiple = TRUE
    )
  ),
  mainPanel()
))

server <- function(input, output) {
  
}

# Run the application
shinyApp(ui = ui, server = server)

当 multiple 为真时，如何限制用户可以 select 使用 selectInput in R shiny 的选项数量？

How to limit the number of options a user can select with selectInput in R shiny when multiple is true?

r

shiny

shinydashboard

selectinput