title: how to label x-axis using python matplotlib
body: <p>I am trying to make a graph from my csv data file. My code is as follow:</p>
  
  <pre><code>for name in per_data.dtype.names[2:]:
      plt.plot(per_data['RELEASE'],per_data[name],label=name)
      plt.legend(loc='upper left',prop = {'size':7},bbox_to_anchor=(1,1))
      plt.tight_layout(pad=5)
      plt.xlabel ('Release')
      plt.ylabel ('Time/Sec')
      plt.title ('Ingest Performance Test')
      plt.grid()
      plt.show() 
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/sqjEp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/sqjEp.png" alt="enter image description here"></a></p>
  
  <p>my csv data is:</p>
  
  <pre><code>DATE    RELEASE 10GB    100GB   200GB   400GB   600GB   800GB   1000GB
  5/5/16  2.67    0.36    4.18    8.54    18      27      38      46
  5/5/16  2.68    0.5     4.24    9.24    18      27      37      46
  5/6/16  2.69    0.32    4.3     9.18    19      29      37      46
  5/6/16  2.7     0.35    4.3     9.3     19      28      37      46
  5/6/16  2.71    0.3     4.18    8.18    16      24      33      41
  </code></pre>
  
  <p>as you can see, I am using the 2nd column -- RELEASE as my x-axis label. The issue is: the actual release numbers are: 2.67, 2.68, 2.69 ,2.70, 2.71
  However, in the graph the program added extra point (2.65, 2.75, 2.85, 2.95, and 2.705). How do I set it so the label of x-axis will reflect my release number?</p>