title: Arrays of strings into numpy.amax
body: <p>In the Python's standard <a href="http://docs.python.org/library/functions.html#max" rel="nofollow"><code>max</code></a> function (I also can pass in a key parameter):</p>
  
  <pre class="lang-py prettyprint-override"><code>s = numpy.array(['one','two','three'])
  max(s) # 'two' (lexicographically last)
  max(s, key=len) # 'three' (longest string)
  </code></pre>
  
  <p>With a larger (multi-dimensional) array, I can not longer use <code>max</code>, so I tried to use <a href="http://docs.scipy.org/doc/numpy/reference/generated/numpy.amax.html" rel="nofollow"><code>numpy.amax</code></a>, however I can't seem to be able to use <code>amax</code> with strings...</p>
  
  <pre class="lang-py prettyprint-override"><code>t = np.array([['one','two','three'],['four','five','six']])
  t.dtype # dtype('|S5')
  numpy.amax(t, axis=0) #Error! Hoping for: [`two`, `six`]
  
  Traceback (most recent call last):
      File "&lt;stdin&gt;", line 1, in &lt;module&gt;
      File "/usr/lib/python2.7/dist-packages/numpy/core/fromnumeric.py", line 1833, in amax
          return amax(axis, out)
  TypeError: cannot perform reduce with flexible type
  </code></pre>
  
  <p>Is it possible to use <code>amax</code> (<em>am using it incorrectly!</em>), or is there some other <code>numpy</code> tool to do this?</p>