title: Ploting Matplotlib Histogram in python
body: <p>I faced an error when I tried to plot histogram in python.
  Could you please help me to solve this error?
  I think it is not a big issue, but I can find the solution yet. :( </p>
  
  <p>Code</p>
  
  <pre><code>import matplotlib.pyplot as plt
  import csv
  import sys
  
  def analyze():
  #   datafile = 'test.csv'
      datafile = sys.argv[1]
      pieces = []
      with open(datafile, 'rt') as f:
          data = csv.reader(f,delimiter = '\t')
          for d in data:
              pieces.append(d)
  
      x = [op for op, response, interval in pieces]
      y1 = [interval for op, response, interval in pieces]
  
  
      plt.figure()
      plt.hist(y1)
      plt.show()
  
  if __name__ == '__main__':
      analyze()
  </code></pre>
  
  <p>Error Message :</p>
  
  <pre><code> File "./scripts/plot_histo.py", line 27, in &lt;module&gt;
      analyze()
    File "./scripts/plot_histo.py", line 23, in analyze
      plt.hist(y1)
    File "/usr/local/anaconda2/lib/python2.7/site-packages/matplotlib/pyplot.py", line 2958, in hist
      stacked=stacked, data=data, **kwargs)
    File "/usr/local/anaconda2/lib/python2.7/site-packages/matplotlib/__init__.py", line 1812, in inner
      return func(ax, *args, **kwargs)
    File "/usr/local/anaconda2/lib/python2.7/site-packages/matplotlib/axes/_axes.py", line 5995, in hist
      if len(xi) &gt; 0:
  TypeError: len() of unsized object
  </code></pre>
  
  <p>Data file format :</p>
  
  <pre><code>653070                232.93               104981.00
  653071                277.94               104981.00
  653072                232.93                12695.00
  653073                232.93                25878.00
  653074                232.93                32714.00
  653075                232.93                19532.00
  653076                232.93                19532.00
  653077                232.93                32715.00
  653078                232.93                32715.00
  653079                232.93                45899.00
  653080                232.93                65430.00
  653081                232.93                65430.00
  Continued .......
   ..........
  </code></pre>