根据另一个输入限制闪亮的应用程序输入

我有一个基本的闪亮应用程序可以评估A + B:

library(shiny)

ui <- fluidPage(
    numericInput(inputId = "A", label = "A", value = 5, step = 1),
    sliderInput(inputId = "B", label = "B", min = 0, max = 10, value = 5),
    textOutput(outputId = "value")
)

server <- function(input, output) {
    output$value <- renderText(paste0("A + B = ", input$A + input$B))
}

shinyApp(ui = ui, server = server)

A is a numericInput值和B is a sliderInput value.

我想限制我的应用程序，以便最大输入值B始终为 2 *A。因此，我必须更改硬编码max = in sliderInput到一些可以动态的东西。我怎样才能做到这一点？

Thanks

您可以致电updateSliderInput更改 B 的最大值observe每当 A 发生变化时就会触发：

library(shiny)

ui <- fluidPage(
  numericInput(inputId = "A", label = "A", value = 5, step = 1),
  sliderInput(inputId = "B", label = "B", min = 0, max = 10, value = 5),
  textOutput(outputId = "value")
)

# Notice the session argument to be passed to updateSliderInput
server <- function(input, output, session) {
  output$value <- renderText(paste0("A + B = ", input$A + input$B))
  observe(updateSliderInput(session, "B", max = input$A*2))
}

shinyApp(ui = ui, server = server)