title: plot data from CSV file with matplotlib
body: <p>I have a CSV file at <code>e:\dir1\datafile.csv</code>.
  It contains three columns and 10 heading and trailing lines need to be skipped.
  I would like to plot it with numpy.loadtxt(), for which I haven't found any rigorous documentation.</p>
  
  <p>Here is what I started to write from the several tries I found on the web.</p>
  
  <pre><code>import matplotlib as mpl
  import numpy as np
  import matplotlib.pyplot as plt
  import matplotlib.cbook as cbook
  
  def read_datafile(file_name):
      # the skiprows keyword is for heading, but I don't know if trailing lines
      # can be specified
      data = np.loadtxt(file_name, delimiter=',', skiprows=10)
      return data
  
  data = read_datafile('e:\dir1\datafile.csv')
  
  x = ???
  y = ???
  
  fig = plt.figure()
  
  ax1 = fig.add_subplot(111)
  
  ax1.set_title("Mains power stability")    
  ax1.set_xlabel('time')
  ax1.set_ylabel('Mains voltage')
  
  ax1.plot(x,y, c='r', label='the data')
  
  leg = ax1.legend()
  
  plt.show()
  </code></pre>