makeaifilter.sci

来自「小波分解源代码」· SCI 代码 · 共 50 行

function Filt = MakeAIFilter(D)
// MakeAIFilter --  Filters for Average-Interpolating Wavelets
//  Usage
//    Filt = MakeAIFilter(D)
//  Inputs
//    D         Degree of polynomial for average-interpolation.
//              Must be an even integer.
//  Outputs
//    Filt      Average-Interpolating Filter suitable for use by
//              AIRefine, FWT_AI, IWT_AI, AIRefine2d, etc.
//
//  Description
//    Calculates average-interpolating filters of various orders
//    which may be used with FWT_AI and related tools.
//
//  See Also
//    AIRefine, FWT_AI, AIRefine2d
//
//  Copyright Aldo I Maalouf

if rem(D,2) | D < 2,
   Filt = [];
else

	// step 1. Moment matrix Mmat

	Mmat = zeros(D+1,D+1);
	for kp1 = 1:(D+1),
	   for lp1 = (-D/2+1):(D/2+1),
			Mmat(lp1+D/2,kp1) = (lp1^kp1 - (lp1-1)^kp1)/kp1;
	   end
	end
	Minv = inv(Mmat);   

	// step 2. Imputation matrix Jmat
	Jmat = zeros(2,D+1);
	for kpp1 = 1:(D+1),
	  for kp1 = 1:2,
			Jmat(kp1,kpp1) = 2 * ((kp1/2)^kpp1 - (kp1/2 - .5)^kpp1)/(kpp1);
	  end
	end

	// step 3. Compose for prediction matrix:
	Pmat = Jmat * Minv ; Pmat = Pmat(2:-1:1,:);
	Filt = Pmat(:);

end
endfunction