title: Matplotlib how to dotplot variable number of points over time?
body: <p>I'm trying to build an audiofingerprint algorithm like Shazam.</p>
  
  <p>I have a variable length array of frequency point data like so:</p>
  
  <pre><code>[[69, 90, 172],
   [6, 18, 24],
   [6, 18],
   [6, 18, 24, 42],
   []
  ...
  </code></pre>
  
  <p>I would like to dotplot it like a spectrogram sort of like this. My data doesn't explicitly have a time series axes but each row is a 0.1s slice of time. I am aware of plt.specgram.</p>
  
  <p><a href="https://i.stack.imgur.com/RTiTy.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RTiTy.png" alt="dotplot"></a></p>