title: Reading excel file into R and Merging all the sheets in it into a single dataframe
body: <p>I have a excel sheet with varying number of sheets in it (it can have 2 sheets or 3 sheets or just depends on the user).
  Headers of all the sheets are same. (first two rows are considered as headers)</p>
  
  <p>I want to merge all these sheets and put it into a single dataframe.</p>
  
  <p>The files are of .xlsx format. and each sheets contain huge number of rows (30 columns and 8000 rows).</p>
  
  <p>I am a beginner in reading excel files in R. I am going through them, in the mean time if anyone knows how to implement this please let me know.</p>
  
  <p>An example of Excel sheet is something like this <a href="https://drive.google.com/file/d/0B54s5NXDypdMaVF5QjVxeG4wUDA/view?usp=sharing" rel="nofollow">Data</a></p>
  
  <p>PS: I want to implement all this in shiny. so, please do mention if there is any efficient method for shiny.</p>
  
  <p><strong>ui.R</strong></p>
  
  <pre><code>fileInput('file2', h5('Choose Your Observation Data'), accept=c('text/csv','text/comma-separated-values,text/plain','.xlsx'))
  </code></pre>
  
  <p><strong>server.R</strong></p>
  
  <pre><code>b &lt;- reactive({
     fileinput2 &lt;- input$file2
     if (is.null(fileinput2))
     return(NULL)
     #xlfile &lt;- list.files(pattern = ".xlsx")
     xlfile &lt;- fileinput2[1]
     wb &lt;- loadWorkbook(xl_file)
     sheet_ct &lt;- wb$getNumberOfSheets()
     b &lt;- rbindlist(pblapply(1:sheet_ct, function(x) {
       res &lt;- read.xlsx(xl_file, x)
     }), fill=TRUE)
     b &lt;- b [-c(1),]
     print (b)
     })
  </code></pre>