This is likely the best you can do:
xv = linspace(min(x), max(x), numel(x));
yv = linspace(min(y), max(y), numel(y));
[Xm,Ym] = ndgrid(xv, yv);
Zm = griddata(x, y, z, Xm, Ym);
figure
contourf(Xm, Ym, Zm)
grid
This creates monotonically-increading vectors from the original ‘x’ and ‘y’ vectors using linspace, creates corresponding matrices using ndgrid, then interpolates them using griddata to create the matrices necessary for the contour function. (The grid call is optional.)
