function nll = nllicaU(w,X, beta)
%
% function returns unnormalized negative log likelihood of ICA model 
% using a Generalized Gaussian distribution with parameter beta in 2-d.
%
% input
%       w: vectorized form of unmixing matrix W
%       X: data matrix
%       beta: parameter of Generalized Gaussian distribution 
% output
%       nll: negative log likelihood

W = reshape(w,2,2);
N = size(X,2);
l = N*log(abs(W(1,1)*W(2,2)-W(1,2)*W(2,1))) + sum(sum(-abs(((W*X).^beta))));
nll = -l;