title: Group by with numpy.mean
body: <p>How do I calculate the mean for each of the below workerid's?  Below is my sample NumPy ndarray.  Column 0 is the workerid, column 1 is the latitude, and column 2 is the longitude.<br>
  I want to calculate the mean latitude and longitude for each workerid.  I want to keep this all using NumPy (ndarray), without converting to Pandas.</p>
  
  <pre><code>import numpy
  from scipy.spatial.distance import cdist, euclidean
  import itertools
  from itertools import groupby
  
  class WorkerPatientScores:
  
      '''
      I read from the Patient and Worker tables in SchedulingOptimization.
      '''
      def __init__(self, dist_weight=1):
          self.a = []
  
          self.a = ([[25302, 32.133598100000000, -94.395845200000000],
                     [25302, 32.145095132560200, -94.358041585705600],
                     [25302, 32.160400000000000, -94.330700000000000],
                     [25305, 32.133598100000000, -94.395845200000000],
                     [25305, 32.115095132560200, -94.358041585705600],
                     [25305, 32.110400000000000, -94.330700000000000],
                     [25326, 32.123598100000000, -94.395845200000000],
                     [25326, 32.125095132560200, -94.358041585705600],
                     [25326, 32.120400000000000, -94.330700000000000],
                     [25341, 32.173598100000000, -94.395845200000000],
                     [25341, 32.175095132560200, -94.358041585705600],
                     [25341, 32.170400000000000, -94.330700000000000],
                     [25376, 32.153598100000000, -94.395845200000000],
                     [25376, 32.155095132560200, -94.358041585705600],
                     [25376, 32.150400000000000, -94.330700000000000]])
  
          ndarray = numpy.array(self.a)
          ndlist = ndarray.tolist()
          geo_tuple = [(p[1], p[2]) for p in ndlist]
          nd1 = numpy.array(geo_tuple)
          mean_tuple = numpy.mean(nd1, 0)
          print(mean_tuple)
  </code></pre>
  
  <p>The output of above is:</p>
  
  <blockquote>
    <p>[ 32.14303108 -94.36152893]</p>
  </blockquote>