title: Draw 3x3 square grid in R
body: <p>I got a list of number (n=9) and would like to draw them out in a 3*3 square grid and each grid fill with corresponding number. How can I do this in R without installing additional package e.g. plotrix. Many thanks!</p>
  
  <p><img src="https://suchwildlove.files.wordpress.com/2012/10/grid11.jpg" alt="pic"></p>