It depends what ‘x’, ‘y’ and ‘z’ are, and what you want.
If they are vectors and have sufficient density, this may work:
figure
scatter3(x, y, z, [], z, 'filled')
view(0, 90)
If they are vectors and are gridded, just use reshape to form them into matrices, then use the contour function. If they are not gridded, first use griddata to form them into matrices, then use contour.
It all depends on what you are starting with, and what you want as the end result.
