rng(100)
[X,Y] = meshgrid(-3:3);
V = reshape(randperm(49),[7 7]);
[Xq,Yq] = meshgrid(-3:0.5:3);
Vqi = interp2(X,Y,V,Xq,Yq,'linear');
Vqg = griddata(X,Y,V,Xq,Yq,'linear');
figure
diffdata = Vqg - Vqi;
mesh(Xq,Yq,diffdata)
Vqi(1:3,1:3)
Vqg(1:3,1:3)
isequal((Vqi(1,1) + Vqi(3,1) + Vqi(1,3) + Vqi(3,3))/4,Vqi(2,2))
isequal((Vqi(3,1) + Vqi(1,3))/2,Vqg(2,2))
