title: R: Graph a 2-D function?
body: <p>Suppose I have a function x^2+y^2=1, how can I graph this function in R?</p>
  
  <p>I have tried:
  <a href="http://i.stack.imgur.com/0SAID.png" rel="nofollow">enter image description here</a></p>
  
  <p>but it doesn't work and says:
  <a href="http://i.stack.imgur.com/ApA6P.png" rel="nofollow">enter image description here</a></p>