title: numpy array to ndarray
body: <p>I have an exported pandas dataframe that is now a numpy.array object.</p>
  
  <pre><code>subset = array[:4,:]
  array([[  2.        ,  12.        ,  33.33333333,   2.        ,
           33.33333333,  12.        ],
         [  2.        ,   2.        ,  33.33333333,   2.        ,
           33.33333333,   2.        ],
         [  2.8       ,   8.        ,  45.83333333,   2.75      ,
           46.66666667,  13.        ],
         [  3.11320755,  75.        ,  56.        ,   3.24      ,
           52.83018868,  33.        ]])
  print subset.dtype
  dtype('float64')
  </code></pre>
  
  <p>I was to convert the column values to specific types, and set column names as well, this means I need to convert it to a ndarray.</p>
  
  <p>Here are my dtypes:</p>
  
  <pre><code>[('PERCENT_A_NEW', '&lt;f8'), ('JoinField', '&lt;i4'), ('NULL_COUNT_B', '&lt;f8'), 
  ('PERCENT_COMP_B', '&lt;f8'), ('RANKING_A', '&lt;f8'), ('RANKING_B', '&lt;f8'),
  ('NULL_COUNT_B', '&lt;f8')]
  </code></pre>
  
  <p>When I go to convert the array, I get:</p>
  
  <pre><code> ValueError: new type not compatible with array.
  </code></pre>
  
  <p>How do you cast each column to a specific value so I can convert the array to an ndarray?</p>
  
  <p>Thanks</p>