title: How to know the line joining two points?
body: <p>I have two points and I want to know the line which is joining them.
  I don't want to draw the line.</p>
  
  <p>I want to create a matrix with all the points which formed the line.</p>
  
  <p>In the future, I want to solve if two points belong or not to a shape. And this is the first part.</p>
  
  <p>EDIT: Thanks to everyone!! I've solved my doubts!
  I have to apply the equation of the straight line!</p>
  
  <p>Thanks again!</p>