当多个为真时，如何限制用户可以使用 R Shiny 中的 selectInput 选择的选项数量？答案

【问题标题】：How to limit the number of options a user can select with selectInput in R shiny when multiple is true?当多个为真时，如何限制用户可以使用 R Shiny 中的 selectInput 选择的选项数量？
【发布时间】：2021-11-17 21:38:21
【问题描述】：

我有一个闪亮的应用程序，我希望用户能够选择多个选项 - 但只能选择一定的限制。我找不到限制数量的方法。

下面是一个简单的、可重现的示例。在其中，我是用户，第一个问题最多只能选择 2/4 个选项，第二个问题最多可以选择 3/4，第三个问题可以选择多少（不需要对问题进行编辑） 3).

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)

【问题讨论】：

标签： r shiny shinydashboard selectinput

【解决方案1】：

您可以使用 selectizeInput 代替 selectInput 并使用 options 参数来设置使用 maxItems 的最大允许项目。

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)

【讨论】：