title: Passing multiple columns of a 2D array into a lambda function and returning a single column array
body: <p>I am missing something simple here. I cannot figure out how to pass multiple columns of a 2D  array (matrix) and output them as a single column array.</p>
  
  <p>Here is a simple example:</p>
  
  <pre><code>import numpy as np
  
  Z = lambda x1,x2: (x1*x2 - 3)^2 + 1
  
  # a sample 2D array with 15 rows and 2 columns    
  x= np.arange(30).reshape((15,2))
  
  answer = [Z(i[0],i[1]) for i in x]
  </code></pre>
  
  <p>The last line of code is where my problem lies. I would like the output to be a single column array with 15 rows. </p>
  
  <p>As a final note: My code only uses 2 columns as inputs. If it could be further expanded to a flexible number of columns, it would be greatly appreciated. </p>