Trying out shiny

server.R

cn<-names(USArrests)
cn[3]<-"All"
sn<-rownames(USArrests)
USArrests$state<-sn

shinyServer(function(input, output) {
  output$crime <- renderUI({
    selectInput("crime", "Crime:", choices = as.list(cn), selected=as.list(cn[1]))
  })
  output$murder <- renderUI({
    if(!is.null(input$crime)) {
      if(input$crime==cn[1]){
        selectInput("murder", "Choose States:", choices = as.list(sn), multiple=TRUE, selected=as.list(sn))
      }
    }
  })  
  output$assult <- renderUI({
    if(!is.null(input$crime)) {
      if(input$crime==cn[2]){
        selectInput("assult", "Choose States:", choices = as.list(sn), multiple=TRUE, selected=as.list(sn))
      }
    }
  })
  output$rape <- renderUI({
    if(!is.null(input$crime)) {
      if(input$crime==cn[4]){
        selectInput("rape", "Choose States:", choices = as.list(sn), multiple=TRUE, selected=as.list(sn))
      }
    }
  })
  getdf <- reactive({
    if(!is.null(input$crime)) {
    if(input$crime==cn[1])
      df2 <- subset(USArrests, state %in% input$murder)
    if(input$crime==cn[2])
      df2 <- subset(USArrests, state %in% input$assult)
    if(input$crime==cn[4])
      df2 <- subset(USArrests, state %in% input$rape)
    if(input$crime==cn[3])
      df2 <- USArrests
    }
    list(df2=df2)
  })
  getplot <- reactive({
    if(!is.null(input$crime)) {
    df2<-getdf()$df2
    if(input$crime==cn[1])
      plot(df2$UrbanPop, df2$Murder)
    if(input$crime==cn[2])
      plot(df2$UrbanPop, df2$Assult)
    if(input$crime==cn[3])
      plot(df2)
    if(input$crime==cn[4])
      plot(df2$UrbanPop, df2$Rape)
    }
  })
  output$table <- renderTable({
    values<-getdf()
    values$df2
  })
  output$plot <- renderPlot({
    getplot()
  })
  output$downloadData <- downloadHandler(
    filename ="data.csv", 
    content = function(file) {
      write.csv(getdf(), file, row.names=FALSE)
    })
  output$downloadPlot <- downloadHandler(
    filename = "plot.png",
    content = function(file) {
      png(file)
      getplot()
      dev.off()
    })
})

ui.R

library(shiny)
#runApp("./R/temp")

shinyUI(pageWithSidebar(
  headerPanel('Example'),
  sidebarPanel(
    htmlOutput("crime"),
    htmlOutput("murder"),
    htmlOutput("assult"),
    htmlOutput("rape"),
    br(),
    downloadButton('downloadData', 'Download Data'),
    downloadButton('downloadPlot', 'Download Plot')
  ),
  mainPanel(
    tabsetPanel(
      tabPanel("Plot", plotOutput("plot", height = "7in")),
      tabPanel("Data", tableOutput("table"))
    )
  )
))