title: How to plot classes in R?
body: <p>Good afternoon : </p>
  
  <p>My question is very simple but i failed to find a right solution.</p>
  
  <p>Suppose that i have an array of 3 columns : </p>
  
  <ul>
  <li>Column 1 : X as axis position ( numerical values ) </li>
  <li>Column 2 : Y as axis position ( numerical values )</li>
  <li>Column 4 : identification of object ( ex : vector_1 , vector_2 , etc. )</li>
  <li>Column 4 : a label of classe such as "Class_A" , "Class_B" ,"Class_C".</li>
  </ul>
  
  <blockquote>
    <p>x &lt;- data.frame("x" = 1:3, "Y" = c(4,6,7), "object" = c("John","Dora"
    , "Peter") , "Class"=("Class_A" , "Class_B" ,"Class_C" ) )</p>
  </blockquote>
  
  <p>How can i plot this in R ? </p>
  
  <p>I want that each class have a different color / shape. X &amp; Y are 2d positions.</p>
  
  <p>Thank you a lot.</p>