title: DiagrammeR general flow direction
body: <p>I would like to produce a diagram with DiagramR.</p>
  <p>This is my code</p>
  <pre><code>    require(DiagrammeR)
      grViz(&quot;
      digraph boxes_and_circles {
      node [shape = box,
          fontname = Helvetica]
      A; B; C; D
      B-&gt;A C-&gt;A D-&gt;B
      }
      &quot;)
  </code></pre>
  <p>But I get this result</p>
  <p><a href="https://i.stack.imgur.com/R26rY.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/R26rY.jpg" alt="enter image description here" /></a></p>
  <p>And I need like this one</p>
  <p><a href="https://i.stack.imgur.com/UdwS2.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/UdwS2.jpg" alt="enter image description here" /></a></p>
  <p>How can I set flow direction to up?</p>