In MATLAB, how do I plot irregularly spaced data?

To plot irregularly spaced data in MATLAB, use the TriScatteredInterp command to create a data structure for interpolation.

The example below plots a saddle-shaped surface by interpolating over 100 random data points:

  %Pick random x and y coordinates
  %  and compute z values.
  x = rand(100,1)*10-5;
  y = rand(100,1)*10-5;

  z = x.^2 -y.^2;

  %Construct the interpolant and use to evaluate
  %  zi for values (xi,yi)
  F = TriScatteredInterp(x,y,z);
  ti = -5:.1:5;

  [xi,yi] = meshgrid(ti,ti);
  zi = F(xi,yi);

  %Plot the interpolated surface in black
  plot3(xi,yi,zi,'k');

  %Add the original data points in red
  hold on; plot3(x,y,z,'or'); hold off