title: Unsymmetrical result for an interpolation of two coordinate vectors and one symmetrical assigned value vector
body: <p>I have two coordinate vectors x what is the vector in x-direction and y what is the vector in y-direction and a corresponding z value vector what is called "z".
  I now want to interpolate this non-uniform data to a very fine uniform coordinates grid.
  But somehow the result is not symmetrical although the actual z values are symmetrical:
  <a href="https://i.stack.imgur.com/14Khv.jpg" rel="nofollow noreferrer">See output</a>.
  Anybody does how to solve this simple issue?
  Here is my code:</p>
  
  <pre><code>  x = [0;0;0;0;0;50;50;50;50;50;95;95;95;95;95;100;100;100;100;100;150;150;150;150;150];
    y = [0;250;500;750;1000;0;250;500;750;1000;0;250;500;750;1000;0;250;500;750;1000;0;250;500;750;1000];
  
    XspanVector = 1:1:150;
    YspanVector = 1:1:1000;
  
    [xx,yy] = meshgrid(obsXspanVector,obsYspanVector);
  
    z = [2000 3000 15165 3000 2000 2000 3000 35750519 3000 2000 2000 3000 113059 3000 2000 2000 3000 109117 3000 2000 2000 3000 36863 3000 2000];
  
    % Interpolate to grid
    zz = griddata(x,y,z',xx,yy,'linear');
  
    % Plot
    contourf(xx,yy,10.*log10(zz),'LineColor','none');
  </code></pre>