Demo Radar chart app from http://glimmer.rstudio.com/mbannert/radar_chart/

server.R

data_sets <- c("mtcars")

shinyServer(function(input, output) {
  
  # Drop-down selection box for which data set
  output$choose_dataset <- renderUI({
    selectInput("dataset", "Data set", as.list(data_sets))
  })
  
  # select a car
  output$choose_car <- renderUI({
    selectInput("car","car",as.list(rownames(get(input$dataset))))
  })

  
  # Check boxes
  output$choose_columns <- renderUI({
    # If missing input, return to avoid error later in function
    if(is.null(input$dataset))
      return()
    
    # Get the data set with the appropriate name
    dat <- get(input$dataset)
    colnames <- names(dat)
    
    # Create the checkboxes and select them all by default
    checkboxGroupInput("columns", "Choose columns", 
                       choices  = colnames,
                       selected = colnames)
  })
  
  
  output$radar <- renderPlot({
    source("radar.R")
    webplot(get(input$dataset),
            which(rownames(mtcars) == input$car), y.cols = input$columns,add=F)
  })
  
  # Output the data
  output$data_table <- renderTable({
    # If missing input, return to avoid error later in function
    if(is.null(input$dataset))
      return()
    
    # Get the data set
    dat <- get(input$dataset)
    
    # Make sure columns are correct for data set (when data set changes, the
    # columns will initially be for the previous data set)
    if (is.null(input$columns) || !(input$columns %in% names(dat)))
      return()
    
    # Keep the selected columns
    dat <- dat[, input$columns, drop = FALSE]
    
    # Return first 20 rows
    head(dat, 20)
  })
})

ui.R

shinyUI(pageWithSidebar(
  
  headerPanel("Car Comparison Radar"),
  
  sidebarPanel(
    uiOutput("choose_dataset"),
    uiOutput("choose_car"),
    
    uiOutput("choose_columns"),
    br(),
    a(href = "http://statisticstoproveanything.blogspot.de/2013/11/spider-web-plots-in-r.html",
      "Radar by Alan Vaughn from statisticstoproveanything"),
     br(),
    a(href = "https://gist.github.com/mbannert/9124890/",
      "Find the shiny code gist here.")
    
  ),
  
  
  mainPanel(
    
    plotOutput(outputId = "radar", height = "600px"),
    tableOutput("data_table")    
  )
))

Your app works fine but this code throws me an error on "get(input$dataset)". Do you run this code exactly at glimmer?

Sorry, my mistake/misunderstanding. Errors were warnings, and the radar chart do pops up. Case closed, and thanks for sharing!

hi, tts! I'm having the same problem you had at first. It throws me some errors:
Error in get(input$dataset) : invalid first argument
Warning in file(filename, "r", encoding = encoding) :
cannot open file 'radar.R': No such file or directory
Error in file(filename, "r", encoding = encoding) :
cannot open the connection
Warning in file(filename, "r", encoding = encoding) :
cannot open file 'radar.R': No such file or directory
Error in file(filename, "r", encoding = encoding) :
cannot open the connection

Would you give me a hint how you fixed this? Thanks!!

Okay, I got it. I just had to run together the webplot function available at: http://statisticstoproveanything.blogspot.de/2013/11/spider-web-plots-in-r.html