title: Finding Cross Product to find points above/below a line in MatplotLib
body: <p>I am trying to draw a line in MatPlotLib , and find all points above or below the line depending on the slope.</p>
  
  <p>After reading this <a href="https://stackoverflow.com/questions/3838319/how-can-i-check-if-a-point-is-below-a-line-or-not">post</a>, and reading about Cross Product, I believe this is the best approach for me to check the points.</p>
  
  <p>I am unsure what would be the most optimal way to implement this in python.</p>
  
  <pre><code>v1 = {x2-x1, y2-y1}   # Vector 1
  v2 = {x2-xA, y2-yA}   # Vector 2
  xp = v1.x*v2.y - v1.y*v2.x  # Cross product
  </code></pre>
  
  <p>Has anyone tried implementing something similar ?</p>
  
  <p>Is there some other way for me to find if points on the plot are above or below a line in MatPlotLib ?</p>