search for: finverse

...any given u0, that is find x0(u0), y0(u0) such that v(x0, y0) = max { v(x,y) : u(x,y)=u0}. So my broad question is what tools does R have to help out? A narrower question is whether there is a function that interpolates on a two-dimensional, but irregular grid? If there is one I could interpolate fInverse(u,v) -> (x,y) and then restrict u=u0 (does this make sense?). Another related question deals with efficient tabulation of fInverse(u, v). In my case it is rather expensive to calculate f(x,y) for any single point (few hours of computer time). Is there any algorithm that selects next (x,y) to c...