title: How to handle empty cells in R markdown?
body: <p>I have an R analysis that I want to present in an R markdown table. The table's layout demands some empty cells:</p>
  
  <pre><code>x &lt;- c(1:14)
  
  Header1 | Header2 | Header3  | Header4
  ------- | ------- | -------- | -------
  Label1  | LabelA  | `r x[1]` | `r x[4]`
  Label2  | LabelB  | `r x[2]` | `r x[5]`
          | LabelC  | `r x[3]` | `r x[6]`
          | LabelD  |          | `r x[7]`
  ------- | ------- | -------- | -------                    
  Label3  | LabelA  | `r x[8]` | `r x[11]`
  Label4  | LabelB  | `r x[9]` | `r x[12]`
          | LabelC  | `r x[10]`| `r x[13]`
          | LabelD  |          | `r x[14]`
  </code></pre>
  
  <p>However, those empty cells are causing the layout to break, ie, <code>LabelC</code> appears directly under <code>Label2</code> even though it is supposed to be one column over.</p>
  
  <p>I know, from searching on this issue, that you can't merge table cells in R Markdown. But can I fill those cells with code such that they will present as empty? I tried filling them with <code>r NULL</code> but nothing happened.</p>