title: Wrong values appears... using python matplotlib.ticker (ax.xaxis.set_major_locator)
body: <p>I am having trouble to get the right x-ticks values by using <code>matplotlib.ticker</code> methods. Here is the simple working example to describe my problem.</p>
  
  <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  import matplotlib
  
  ## Sample code
  np.arange(0, 15, 5)
  plt.figure(figsize = [6,4])
  
  x=np.array([1,2,3,4,5,6,7,8,9,10,11,12,13,14,15])
  y=np.array([15,16,17,18,19,20,40,50,60,70,80,90,100,110,120])
  ax = sns.pointplot(x,y, color='k', markers=["."], scale = 2)  
  ax.xaxis.set_major_locator(matplotlib.ticker.FixedLocator([1,5,8]))
  </code></pre>
  
  <p>Results: x-ticks is located at the right position(1,5,8) but the values that I want for those positions are 1,5,8 (corresponding x values) instead of (1,2,3)</p>
  
  <p>I have tried all locators explained in <a href="https://matplotlib.org/examples/ticks_and_spines/tick-locators.html" rel="nofollow noreferrer">https://matplotlib.org/examples/ticks_and_spines/tick-locators.html</a>, but it all shows 1,2,3 x-ticks value... :( </p>
  
  <p><a href="https://i.stack.imgur.com/is3pL.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/is3pL.png" alt="wrongtickvalue"></a></p>
  
  <p>My actual problem (Having trouble of identical issues: x-ticks should be something like 64, 273.5, 1152.5 instead of the first three numbers)</p>
  
  <pre><code>...
  print(intervals}
  &gt;&gt; [64, 74, 86.5, 10.1, 116.0, 132.0, 152.0, 175.5, 204.0, 236.0, 273.5, 319.0, 371.0, 434.0, 509.0, 595.5, 701.0, 861.0, 1152.5]
  
  ax.xaxis.set_major_locator(matplotlib.ticker.LinearLocator(3)
  plt.show()
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/V7FDs.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/V7FDs.png" alt="wrong_tick_value2"></a></p>