library(shiny)
ui = fluidPage(
  sidebarLayout(
    sidebarPanel(
      selectInput("analysis", 
                  label = "Choose a type of exploratory analysis:", 
                  choices = c("Data Summary", "Histogram", "Boxplot"),
                  selected = "Histogram"),
    submitButton("Update View")),
  mainPanel(
      h4("Data Summary"),
      tableOutput("summary"),
      h4("Histogram"),
      plotOutput("Histogram"),
      h4("Boxplot"),
      plotOutput("Boxplot")
    )
  )
)

server = function(input, output) {
  analysisInput <- reactive({
    switch(input$analysis,
           "Histogram" = 1, "Boxplot" = 2, "Data Summary" = 3) })
  output$summary <- renderPrint ({ 
    analysis <- analysisInput()
    if (analysis == 3) {summary(cars)}   })
  output$Boxplot <- renderPlot ({ 
    analysis <- analysisInput()
    if (analysis == 2) {
      boxplot(cars) 
      title(main = "1920s Cars - Boxplot", ylab = "Speed (mph)")} })
  output$Histogram <- renderPlot({
    analysis <- analysisInput()
    if (analysis == 1) {
    par(mfcol= c(1,2), oma=c(4,2,4,2))  
    hist(cars[,1], breaks = 10, col = 'darkgray', border = 'white',
      main = "1920s Cars - Distribution",
      xlab = "Speed (mph)")
    hist(cars[,2], breaks = 10, col = 'darkgray', border = 'white',
      main = "1920s Cars - Distribution",
      xlab = "Distance(ft)") }  
    }) 
}