How Can I do contour plot?

Suppose I have a square figure.

Answer 1

[Walter Roberson]

MATLAB cannot create continuous figures. You could approximate a continuous figure by creating a surf() or a patch() and configure shading and lighting properties. For your purpose I think a surf() would be most appropriate.

[Walter Roberson]

Before you were working with x (monotonically increasing) and with y (a variety of values), and with no Z. That was not enough information to generate a 3D plot.

If you now have x and y coordinates for each of the points, and you have a z (value) for the points as well, then you can use the approaches discussed early on: griddata() or trisurfinterp or scatteredinterpolant. Take the resulting rectangular array of z and surf() it, and set the shading properties of the surface and set up the lighting properties as well.