server.r

# Some pre-computed stuff in R. In this example, just assign values to a var
# data_sets <- c("mtcars", "morley", "rock")

data_sets <- c("mymtcars","mtcars", "morley", "rock")
mymtcars <- mtcars[,1:4]

shinyServer(function(input, output) {

  mymtcars <- mymtcars

  extra2 <- function() {
    dat <- mymtcars
    dat$test <- 1:32
    mymtcars <<- dat
  }

  extra1 <- function() {
    extra2()
  }

  # Drop-down selection box for which data set
  output$choose_dataset <- reactiveUI(function() {
    selectInput("dataset", "Data set", as.list(data_sets))
  })

  # Check boxes
  output$choose_columns <- reactiveUI(function() {
    if(is.null(input$dataset))
      return()

    # Get the data set with the appropriate name
    dat <- get(input$dataset)
    colnames <- names(dat)
    print(colnames)

    extra1()

    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 the data
  output$data_table <- reactiveTable(function() {
    if(is.null(input$dataset) || is.null(input$columns))
      return()

    # Get the data set
    dat <- get(input$dataset)

    # Keep the selected columns
    dat <- dat[, input$columns, drop = FALSE]

    # Return first 20 rows
    head(dat, 20)
  })
})

ui.r

# Define UI for miles per gallon application
shinyUI(pageWithSidebar(

  headerPanel(""),

  sidebarPanel(
    uiOutput("choose_dataset"),

    uiOutput("choose_columns")
  ),


  mainPanel(
    tableOutput("data_table")
  )
))