将 selectInput 存储在 string/character 对象中

Question

我想将 input$var 中的变量存储到一个对象中，该对象可以与后面的字符串进行比较。现在，我只是尝试通过将它存储到一个对象 value_stored 来在屏幕上打印它。但它没有打印任何东西*（错误：无法将类型 'closure' 强制转换为类型 'character'* 的向量）。这意味着它没有存储值。

library(shiny)
ui <- fluidPage(
  titlePanel("censusVis"),

  sidebarLayout(
    sidebarPanel(
      helpText("Create demographic maps with 
               information from the 2010 US Census."),

      selectInput("var", 
                  label = "Choose a variable to display",
                  choices = c("Percent White", 
                              "Percent Black",
                              "Percent Hispanic", 
                              "Percent Asian"),
                  selected = "Percent White")
      ),

    mainPanel(
      textOutput("selected_var")
      textOutput("test")
    )
  )
  )

server <- function(input, output) {

  output$selected_var <- renderText({ 
    paste(input$var)
  })

  value_store <- reactive(input$var)

  output$test <- renderText({
   paste(value_store) 
  })

  # I want to use the value in input$var for some comparision. 
  # but value_store unable to store. Help.

}


shinyApp(ui = ui, server = server)

Answer 1

我强烈建议使用 reactiveValues（对象来存储您的反应值）和 observeEvent。

使用服务器代码：

server <- function(input, output) {
    # Create object for reactive values 
    rv <- reactiveValues(
        value_store = character()
    )
    # When input changes -> update
    observeEvent(input$var, {
        output$selected_var <- renderText({ 
            paste(input$var)
        })
        rv$value_store <- input$var
        output$test <- renderText({
            paste(rv$value_store) 
        })
    })
}

PS：您可以删除 paste，因为它在那里什么都不做。

Answer 2

你就快完成了，你只需要先定义反应元素，然后在 observeEvent() 函数中观察输入。然后在观察中使用 isolate() 来更新值。

ui <- fluidPage(
  titlePanel("censusVis"),

  sidebarLayout(
    sidebarPanel(
      helpText("Create demographic maps with 
           information from the 2010 US Census."),

  selectInput("var", 
              label = "Choose a variable to display",
              choices = c("Percent White", 
                          "Percent Black",
                          "Percent Hispanic", 
                          "Percent Asian"),
              selected = "Percent White")
  ),

 mainPanel(
   textOutput("selected_var")
   textOutput("test")
 )
 )
)

server <- function(input, output) {

  value_store <- reactive(val = '')

  observeEvent(input$var, {

    # add to reactive
    isolate(value_store$val = input$var)

    # or render update
    output$selected_var <- renderText({ 
       paste(value_store$val)
     })

  })




 output$test <- renderText({
   paste(value_store$val) 
 })

  # I want to use the value in input$var for some comparision. 
  # but value_store unable to store. Help.

}


shinyApp(ui = ui, server = server)

将 selectInput 存储在 string/character 对象中

Store selectInput in a string/character object

r

shiny

shiny-reactivity