title: data.table::fread Read all worksheets in an Excel workbook
body: <p>My Excel document <code>my.xlsx</code> has two Sheets named <strong>Sheet1</strong> and <strong>Sheet2</strong>. I want to read all worksheets in an Excel workbook using <code>fread</code> function from <code>data.table</code> <code>R</code> package. The following code just read the active worksheet. Wonder how to read all worksheets without knowing their names. Thanks</p>
  
  <pre><code>df3 &lt;- data.table::fread("in2csv my.xlsx")
  &gt; names(df3)
  [1] "A" "B"
  &gt; df3
     A  B
  1: 1  2
  2: 2  4
  3: 3  6
  4: 4  8
  5: 5 10
  </code></pre>