U=VL_TPSU(X,Y) returns the matrix

[ U(|X(:,1) - Y(:,1)|) ... U(|X(:,1) - Y(:,N)|) ] [ ] [ U(|X(:,M) - Y(:,1)|) ... U(|X(:,M) - Y(:,N)|) ]

where X is a 2xM matrix and Y a 2xN matrix of points and U(r) is the opposite -r^2 log(r^2) of the radial basis function of the thin plate spline specified by X and Y.

[U,dU]=vl_tpsu(x,y) returns the derivatives of the columns of U with respect to the parameters Y. The derivatives are arranged in a Mx2xN array, one layer per column of U.

See also: VL_TPS(), VL_HELP().