Flexible upload

server.R

# .libPaths("/home/tian/R/x86_64-pc-linux-gnu-library/3.0")
library(XLConnect)

shinyServer(function(input, output) {  
  chooseFile <- reactive({
    inFile <- input$iFile
    if (!is.null(inFile)) {
      # Determine document format;
      ptn <- "\\.[[:alnum:]]{1,5}$"
      suf <- tolower(regmatches(inFile$name, regexpr(ptn, inFile$name)))
      
      # Options for Excel documents;
      if (suf %in% c('.xls', '.xlsx')) {
        wb <- loadWorkbook(inFile$datapath)
        sheets <- getSheets(wb)
        output$ui <- renderUI({
          list(
            selectInput(inputId = "sheet", label = "Select a sheet:", choices = sheets),
            textInput(inputId = 'arg', label = 'Additional Arguments:', value = ' '),
            tags$hr()
          )
        })
        return(list(path = inFile$datapath, suf = suf))
      } 
      
      # Options for txt documents;
      if (suf %in% c('.txt', '.csv')) {
        output$ui <- renderUI({
          list(
            checkboxInput(inputId = 'header', label = 'First line as header', value = TRUE),
            textInput(inputId = 'sep', label = 'Separator', value = " "),
            textInput(inputId = 'quote', label = 'Quote', value = '\"'),
            textInput(inputId = 'arg', label = 'Additional Arguments:', value = ' '),
            tags$hr()
          )
        })
        return(list(path = inFile$datapath, suf = suf))
      }
    } else {return(NULL)}
  })
  
  
  output$contents <- renderTable({
    objFile <- chooseFile()
    if (!is.null(objFile)) {
      suf <- objFile$suf
      # For Excel documents;
      if (suf %in% c('.xls', '.xlsx')) {
        Sheet <- input$sheet
        if (!is.null(Sheet)){
          
          if (input$arg %in% c(' ', '')) {
            wb <- loadWorkbook(objFile$path)
            dat <- readWorksheet(wb, Sheet)
            return(dat)
          } else {
            wb <- loadWorkbook(objFile$path)
            expr <- paste('readWorksheet(wb, Sheet,', input$arg, ')', sep = '')
            print(expr)
            dat <- eval(parse(text = expr))
            return(dat)
          }
            
        } else {return(NULL)}
      }
      # For .txt and .csv documents;
      if (suf %in% c('.txt', '.csv')) {
        if (is.null(input$header)) {
          dat <- read.table(objFile$path)
          return(dat)
        } else {
          if (input$arg %in% c(' ', '')) {
            dat <- read.table(objFile$path, header=input$header, sep=input$sep, quote=input$quote)
            return(dat)
          } else {
            expr.1 <- paste('"', gsub('\\', '/', objFile$path, fixed = TRUE), '"', sep = '')
            expr.2 <- paste(expr.1, 
                            paste('header =', input$header), 
                            paste('sep =', paste("'", input$sep, "'", sep = '')), 
                            paste('quote =', paste("'", input$quote, "'", sep = '')), input$arg,  sep = ', ')
            print(expr.2)
            expr <- paste('read.table(', expr.2, ')', sep = '')
            print(expr)
            dat <- eval(parse(text = expr))
            return(dat)
          }
        }
      }
      
    } else {return(NULL)}

  })

})

ui.R

shinyUI(pageWithSidebar(
  # Include css file;
  tagList(
    tags$head(
      tags$title("Upload Data"),
      tags$link(rel="stylesheet", type="text/css",href="style.css")
    )
  ), 
  # Control panel;
  sidebarPanel(
    fileInput(inputId = "iFile", label = "", accept="application/vnd.ms-excel"),
    tags$hr(),
    uiOutput(outputId = "ui"),
    submitButton("Upload!")
  ),
  # Output panel;
  mainPanel(tableOutput(outputId = "contents"))
))