title: how can i change the size of a png file with R
body: <p>I am plotting png files and getting a small picture.</p>
  
  <p>Do you know some simple code that can change size of a png plot?</p>
  
  <p>(my plots are too high and too "slim".</p>
  
  <p>In addition is there a way to change resolution of the plot ?</p>
  
  <p>thanks 
  yigeal</p>