title: Python plotting float lists with directional arrows
body: <p>After inspiring from this answer in <a href="https://stackoverflow.com/questions/7519467/line-plot-with-arrows-in-matplotlib">Line plot with arrows in matplotlib</a> , I tried this but not working. </p>
  
  <p>My code: </p>
  
  <pre><code>x = [34.9, 34.9, 34.9, 34.9, 35.7, 34.9, 34.9, 34.1, 34.1, 34.9]
  y = [19.544, 19.544, 16.752, 17.45, 17.85, 17.45, 18.846, 17.05, 15.686, 18.846] 
  
  plt.figure()
  plt.quiver(x[:-1], y[:-1], x[1:]-x[:-1], y[1:]-y[:-1], scale_units='xy', angles='xy', scale=1)
  plt.show()
  </code></pre>
  
  <p>Present output: </p>
  
  <pre><code>TypeError: unsupported operand type(s) for -: 'list' and 'list'
  
  &lt;Figure size 432x288 with 0 Axes&gt;
  </code></pre>