title: Why getting Cross index error using np.ix_
body: <p>Why does this error occur while working with <code>np.ix_</code>?</p>
  <pre><code>import numpy as np
  
  a = np.arange(1,3).reshape(1,2)
  print(a)
  
  k_r = [[1,1],[1,-1]]
  
  r = np.zeros((10,10),int)
  r[np.ix_([a],[a])]= k_r
  
  print(r)
  </code></pre>
  <p>Error:</p>
  <blockquote>
  <p>ValueError: Cross index must be 1 dimensional</p>
  </blockquote>