Thin plate spline	$f(x)=x^2{\log }_{2}x$	(1)
Cubic function	$f(x)=x^3$	(2)
Multiple quadratic function	$f(x)={\left(x^2+c^2\right)}^k,0<k<1$	(3)
Inverse multiple quadratic function	$f(x)={\left(x^2+c^2\right)}^{-k},0<k<1$	(4)