title: How to plot 3d parametric equations in R?
body: <p>From the parametric equations on wiki page ( <a href="http://en.wikipedia.org/wiki/Parametric_equation" rel="nofollow noreferrer">http://en.wikipedia.org/wiki/Parametric_equation</a>  ), I can plot 2d equations as follows: </p>
  
  <pre><code>#for a circle: 
  x = seq(-pi, pi, length.out=30)
  plot(sin(x),cos(x))
  
  # for a star: 
  a=10; b=10/1.8
  x=seq(-50,50,length.out=500)
  plot((a-b)*cos(x)+b*cos(x*((a/b)-1)), (a-b)*sin(x)-b*sin(x*((a/b)-1)), ylim=range(-13,13))
  </code></pre>
  
  <p>How can I plot 3d equations on a 3d plot of a Helix given by equations: </p>
  
  <pre><code>x=a*cos(t)
  y=a*sin(t)
  z=b*t
  </code></pre>
  
  <p>From searching I found that the 3d plotting functions take either a matrix or x,y,z values but not math curve functions.</p>