title: plotting numpy.ndarray
body: <p>I do n-operations on matrices which results in the output of n of 2x1 matrices. I append them to a list and want to plot as points with x,y coordinate. I found I need to convert them to a numpy.array so I finish with nx2 ndarray and want to plot <code>[:0]</code> and <code>[:1]</code>. When I print results everything seems to be correct when I try to plot I finish with blank figure and no points at all. I noticed that ndarrays are separated by space not by comma but not sure how to interpret it. My code looks like:</p>
  
  <pre><code>import numpy as np
  import pylab as pl
  
  class GetMat(object):
      def __init__(self):
          self.Posp = np.matrix([[1,1],[1,1]])
          self.Velp = np.matrix([[1],[1]])
      def __call__(self):
          self.Posp = self.Posp*np.random.random()
          self.Velp = self.Velp*np.random.random()
          return self.Posp,self.Velp
      def __repr__(self):
          return "Posp = \n%s \nVelp = \n%s" % (self.Posp,self.Velp)
  class Data(object):
      def __init__(self):
          self.x = 0
      def __call__(self,P,V):
          self.x = P*V
          return self.x[0,0], self.x[1,0]
      def __repr__(self):
          return "x = %s" % self.x
  
  def Test():
      Nsamples = np.arange(0,10,1)
      newMat = GetMat()
      dataToPlot = Data()
      Xsaved = []
      for i in range(len(Nsamples)):
          z1,z2 = newMat()
          position, velocity = dataToPlot(z1,z2)
          Xsaved.append([position, velocity])
      print 'Xsaved = %s' % Xsaved
      print 'tyep Xsaved %s' % type(Xsaved)
      XsavedArr = np.array(Xsaved)
      print 'XsavedArr %s' % XsavedArr
      print 'tyep XsavedArr %s' % type(XsavedArr)
      print 'XsavedArr[:,0] = %s' % XsavedArr[:,0]
      print 'XsavedArr[:,1] = %s' % XsavedArr[:,1]
      pl.plot(np.array(XsavedArr[:,0]),np.array(XsavedArr[:,1]), linestyle='x-',label = 'Xsaved')
      pl.show()
  
  if __name__ == '__main__':
      Test()      
  </code></pre>
  
  <p>I expect normal plot of random numbers not a blank. I can't find how to plot having ndarrays in form of nx2 matrix</p>