title: How to arrange matplotlib scatters one over another by scale
body: <p>I have 2 inputs (x,y) and 3 classes for that inputs which i mark by different colors. Using scaling I can see how many times does particular class is found at particular (x,y) point.</p>
  <p>To show points on the chart i use such code:</p>
  <pre><code>ax.scatter(first_column, second_column, c=outputs_colors, s=labels_mean, alpha=0.3)
  
  
  first_column - x_values; 
  second_column - y_values; 
  c=outputs_colors - colors for different classes; 
  s=labels_mean - class share at a given point
  </code></pre>
  <p>When x,y inputs are various floats - the charts are informative:
  <a href="https://i.stack.imgur.com/cZcWP.png" rel="nofollow noreferrer">Plot Scatter Image 1</a></p>
  <p>But when x,y are integers and there are many overlaps in classes the chart loses clarity: <a href="https://i.stack.imgur.com/xEvOw.png" rel="nofollow noreferrer">Plot Scatter Image 2</a></p>
  <p>Is it possible to arrange scatters by size from bigger as background to smaller as foreground without using loop and separate plot.scatter for each class? To get something like this:
  <a href="https://i.stack.imgur.com/hCOQg.png" rel="nofollow noreferrer">Plot Scatter Image 3</a></p>