title: How do i replace nan in 2d array with other 2d array value
body: <p>For example, I have on 2d array named c.</p>
  
  <pre><code>&gt;&gt;&gt; c = numpy.array([[1,np.nan,3],[4,5,6],[7,8,9]])
  &gt;&gt;&gt; c
  array([[  1.,  nan,   3.],
         [  4.,   5.,   6.],
         [  7.,   8.,   9.]])
  </code></pre>
  
  <p>other named as b.</p>
  
  <pre><code>&gt;&gt;&gt; b
  array([[1, 0, 1],
         [0, 0, 0],
         [1, 0, 1]])
  </code></pre>
  
  <p>In in the array index c[0][1] there is nan i want to replace it with b[0][1]. without using for loop.</p>
  
  <p>Is there any method in numpy which will enable me to do so?</p>
  
  <p>I want the result to look like following. </p>
  
  <pre><code>&gt;&gt;&gt; c
  array([[ 1.,  0.,  3.],
         [ 4.,  5.,  6.],
         [ 7.,  8.,  9.]])
  </code></pre>