x=0:0.1:1;
y=0:0.2:2;
[X,Y]=meshgrid(x,y);
z=X.^2+Y.^2;
interp2(x,y,z,0.5,0.5)
interp2(x,y,z,[0.5,0.6],0.5)
interp2(x,y,z,[0.5,0.6]',[0.4,0.5])
interp2(x,y,z,[0.5,0.6]',[0.4,0.5],'spline')