I have lists of triples `{{x1, y1, f[x1,y1]},{x2, y2, f[x2,y2]},... }`, which I would like to interpolate. In order to use Interpolation[], I seem to need a list structure such as `{{{x1, y1}, f[x1,y1]},{{x2, y2}, f[x2,y2]},...}`. How can I convert the original lists to the required new structure? Is there an alternative way of using Interpolation[] on the original lists?