title: Merging two arrays by column
body: <p>let's say I have two numpy arrays <code>a = (n x m)</code> and <code>b = (z x m)</code> where columns m are some common identifier. </p>
  
  <pre><code>a = np.array([[1, 0, 0, 1], [0, 1, 0, 1], [0, 0, 0, 1], [1, 1, 0, 1]])
  b = np.array([[1, 0, 0, 1], [1, 1, 0, 1], [0, 1, 1, 0]])
  </code></pre>
  
  <p>is there a numpy-ish way to get <code>c = (n x z)</code> where <code>c_ij = 1 if (any element in (row i of a AND row j of b) is equal to 1) else 0</code> without loops, so in this case</p>
  
  <pre><code>c = np.array([[1, 1, 0], [1, 1, 1], [1, 1, 0], [1, 1, 1]])
  </code></pre>