Slow and steady win the race - The shelf

Ottavia M. Epifania

What went wrong:

appExamples/broken-shelf.R

• UI
• Server
• Together

ui <- fluidPage(
    sidebarLayout(sidebarPanel(
        selectInput(inputId = "dataset",
                    label = "Choose a dataset:",
                    choices = list("rock" = 1, 
                                   "pressure" = 2,
                                   "cars" = 3)), 
      actionButton("load", "Select dataset")
    ),
    mainPanel(
        plotOutput(
          "graph"   
        ), 
        verbatimTextOutput( 
          "summary"   
    ))))

server <- function(input, output){
 values <- reactiveValues()
  dataInput <- reactive({
    if(input$dataset == 1){
      data <- rock
    } else if (input$dataset == 2 ){
      data <- pressure
    } else if (input$dataset == 3) {
      data <- cars
    }
  })
  observeEvent(input$load, { 
    values$data <- data.frame(dataInput())
  })

  output$graph <- renderPlot({
    plot(values$data[, c(1:2)])
  })

  output$summary <- renderPrint({
    summary(values$data)
  })
}

shinyApp(ui, server)

Just…don’t scare the users

Choose a dataset:

rock pressure cars

The code

• UI
• Server
• Together

ui <- fluidPage( # same as before
   sidebarLayout(
    sidebarPanel(
      selectInput(inputId = "dataset",
                  label = "Choose a dataset:",
                  choices = list("rock" = 1, 
                                "pressure" = 2,
                                "cars" = 3)),

      actionButton("load", "Upload data")
      ),
    mainPanel(
      plotOutput(
        "graph"
      ),
      verbatimTextOutput(
        "summary"
      )
    ) 
  )
)

server <- function(input, output){
   values <- reactiveValues()
    dataInput <- reactive({
      if(input$dataset == 1){
        data <- rock
      } else if (input$dataset == 2 ){
        data <- pressure
      } else if (input$dataset == 3) {
        data <- cars
      }
    })
observeEvent(input$load, {
      values$data <- data.frame(dataInput())
})
output$graph <- renderPlot({
    validate(need(input$load > 0, "Waiting for data"))
    plot(values$data[, c(1:2)])
  })
output$summary <- renderPrint({
    validate(need(input$load > 0, "Waiting for data"))
    summary(values$data)
  })
}

shinyApp(ui, server)