Gradient for scattered data

[dFx,dFy] = TRIGRADIENT(TRI,X,Y,Z) or TRIGRADIENT(TRI,X,Y,Z,'vertex') returns numerical gradients of the function z = F(x,y), dFx = dF/dx and DFy = dF/dy at the vertices of the triangles specified in TRI. dFx and dFy are column vectors having the same number of elements as X,Y, and Z.

[dFx,dFy] = TRIGRADIENT(TRI,X,Y,Z,'face') returns the numerical gradients that are constant over each triangle face. In this case, dFx and dFy are column vectors having M = size(TRI,1) elements.