title: How to get full circle instead of getting a major sector of it down here?
body: <p>I am trying to contour plot pressure at a given height (z=34) where I already have the 3D pressure data (P, varying with r &amp; z, independent of theta).</p>
  
  <p>I am using the following command for doing so, but a sector of the the circle doesn't appear.</p>
  
  <pre><code>n=50;
  theta = linspace(0,2*pi,n-6);
  r = linspace(0.01,5,n+1);
  [R,th] = meshgrid(r(2:n-5),theta);
  [x1,y1] = pol2cart(R,th);
  contour(x1,y1,P(:,:,34))
  </code></pre>
  
  <p>What shall I do to make it full circle?
    <img src="https://i.stack.imgur.com/OfOMz.jpg" alt="enter image description here"></p>