title: Unexpected venneuler output
body: <p>I'm trying to understand how <code>venneuler</code> works and it outputs a venn diagram I wouldn't expect.  I like to work with simple examples when I'm trying to understand something.  I'm supplying the matrix below which I believe is :</p>
  
  <blockquote>
    <p>a logical or numeric matrix whose columns represent sets and
    co-occurrence is 
        defined by non-zero (rep. TRUE) values in rows (weight for a row being 1 for 
        logical matrices or the row sum for numeric matrices). -venneular manual-</p>
  </blockquote>
  
  <p>I would expect if two things both have 1's or 0's in the same row they'd have overlap in their venn.  So in this matrix w and z have no 1's or 0's in common.  I'd expect their venn's not to overlap but they do (see figure 1 below).  Why?  If I'm supplying wrong information or it needs to be reformatted please explain.  If it's in the calculations of <code>venneular</code> please explain that.</p>
  
  <pre><code>     w x y z
  [1,] 1 0 1 0
  [2,] 0 0 1 1
  [3,] 0 0 1 1
  [4,] 1 1 0 0
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/KAUZ8.png" alt="https://dl.dropbox.com/u/61803503/venn.1.png"></p>
  
  <p>The code for the above:</p>
  
  <pre><code>library(venneuler)
  w &lt;- c(1,0,0,1)
  x &lt;- c(0, 0, 0, 1)
  y &lt;- c(1, 1, 1,0)
  z &lt;- c(0, 1, 1,0)
  a &lt;- cbind(w, x, y, z)       
  v &lt;- venneuler(a)
  plot(v)
  </code></pre>