title: Histogram bars cannot stacked using matplotlib in python
body: <p>I have implemented a histogram plot using &quot;matplotlib&quot; in python. I have two variables x1 and x2 with 15 elements in each. when running the code, the histogram bars are not stacked instead they are overlapped, as shown in the figure below.</p>
  <p>I want to plot a stacked histogram of the bars of the variables.</p>
  <p><strong>The is the code:</strong></p>
  <pre><code>x1= [23, 25, 40, 35, 40, 53, 33, 28, 55, 34, 20, 37, 36, 23, 33]
  x2= [36, 20, 27, 50, 34, 47, 18, 28, 52, 21, 44, 34, 13, 40, 49]
  colors = ['blue', 'orange']
  bins = [10,20,30,40,50,60]
  fig, (ax0, ax1, ax2) = plt.subplots(nrows=3)
  
  ax0.hist(x1,bins = bins,  histtype='bar',  label=colors[0], rwidth=0.8)
  ax0.hist(x2,bins, histtype='bar', stacked=True, label=colors[1], rwidth=0.8)
  
  ax1.hist(x1, bins = bins, histtype='bar',  label=colors[0], rwidth=0.8)
  ax1.hist(x2,bins = bins, histtype='bar', stacked=True,  label=colors[1], rwidth=0.8)
  
  ax2.hist(x1, bins = bins, histtype='bar',  label=colors[0], rwidth=0.8)
  ax2.hist(x2,bins = bins, histtype='bar', stacked=True,  label=colors[1], rwidth=0.8)
  
  plt.show()
  </code></pre>
  <p><strong>Output</strong>
  <a href="https://i.stack.imgur.com/aRiWw.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/aRiWw.png" alt="enter image description here" /></a></p>