title: How to plot points using their class labels?
body: <p>I have a 100 2-dim points, which form a 100 by 2 matrix X, stored in a text file "data"</p>
  
  <p>I have a 100-dim vector Y, which form the class labels (numerical from 1 to 3) of the 100 points, and is stored in a text file "labels".</p>
  
  <p>In R, I was wondering how you would plot the 2-dim points in X, s.t. each point is represented by its class label instead of a dot and represented in a color of its class label (the color is same for points of the same class label, but different for points of different class labels)?</p>
  
  <p>Thanks!</p>