Question

我希望每次增加 actionButton 时变量 x 的值都增加 1，例如，请参见下面的可重现代码。但是observeEvent里面的代码是隔离的，x的值不会增量更新。

library(shiny)

ui <- fluidPage(
  actionButton("plus","+1"),
  textOutput("value")
)

server <- function(input, output, session) {
  x = 1
  observeEvent(input$plus,{
    x = x+1
    output$value = renderText(x)
  })
}

shinyApp(ui, server)

Answer 1

您需要确保要更改的值是响应式的。您可以使用 x 使 reactiveVal() 具有反应性。然后，当您想要 x 的当前值时调用 x()，当您想要更改 x 的值时，您使用 x(<new value>)

library(shiny)

ui <- fluidPage(
  actionButton("plus","+1"),
  textOutput("value")
)

server <- function(input, output, session) {
  x = reactiveVal(0)
  observeEvent(input$plus,{
    x(x()+1) # increment x by 1
  })
  output$value = renderText(x())
}

shinyApp(ui, server)

Answer 2

这是一个简单的计数器：参见此处：https://gist.github.com/aagarw30/69feeeb7e813788a753b71ef8c0877eb

library(shiny)

# Define UI for application
ui <- fluidPage(

    # Application title
    titlePanel("Counter"),


        # Show button and text
        mainPanel(
            actionButton("add1", "+ 1"),
            br(),
            textOutput("count")
        )
    )

# Define server logic required to draw a histogram
server <- function(input, output) {

    counter <- reactiveValues(countervalue = 0) # Defining & initializing the reactiveValues object
    
    observeEvent(input$add1, {
        counter$countervalue <- counter$countervalue + 1   # if  the add button is clicked, increment the value by 1 and update it
    })
    
    output$count <- renderText({
        paste("Counter Value is ", counter$countervalue)   # print the latest value stored in the reactiveValues object
    })
}

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

每次单击 actionButton 时，R 闪亮变量增加 1

2 个答案: