title: "read_excel" in a Shiny app
body: <p>I have a Shiny app that uses the <code>read.xlsx</code> function from package <code>xlsx</code>. All works fine, but I want to change to <code>read_excel</code> from <code>readxl</code>, hoping it would be faster and able to cope with large files.</p>
  
  <p>ui part:</p>
  
  <pre><code>fileInput("inputFile","Upload file...")
  </code></pre>
  
  <p>server part:</p>
  
  <pre><code>  data &lt;- reactive({
      inFile &lt;- input$inputFile
      if (is.null(inFile)) { return(NULL) }    
      dataFile &lt;- read_excel(inFile$datapath,sheet=1)
      return(dataFile)
    })
  </code></pre>
  
  <p>I get the "Unknown format" error.</p>
  
  <blockquote>
    <p>inFile$datapath is "/tmp/.../60974676c7287e913d1c0dc5/0" <br>
    inFile$type is "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"</p>
  </blockquote>
  
  <p>Question 1: is there a way to tell <code>read_excel</code> that it's a xlsx type file?<br>
  Question 2: is it possible to control the location where the uploaded file will be stored?</p>