title: I am getting a wrong output for numpy.sum
body: <p>I have the variable X of the type numpy.ndarray</p>
  
  <pre><code>X = 
  [[ 0.44381946  0.27899923  0.4949196 ]
   [ 0.84257149  0.30482022  0.62306499] 
   [ 0.59696025  0.36293078  0.42723482]
   [ 0.85710666  0.61489953  0.58918237]
   [ 0.99383178  0.88306841  0.85875682]] 
  </code></pre>
  
  <p>When I use numpy.sum(X , axis=1) to sum along the columns, I get this as output</p>
  
  <pre><code> [-2.7922436  -1.83243432 -2.37986939 -1.16950882 -0.28280943]
  </code></pre>
  
  <p>which is clearly wrong (there are no negative numbers in X). What am I doing wrong?</p>