function [z, a, b, alpha, err] = algellipse (X, W, show);%ALGELLIPSE     Algebraic least square ellipse fit%%       [z, a, b, alpha, err] = ...%         algellipse (X, W{default ones}, show{default 0})%       fits an ellipse by minimizing the "algebraic distance"%       in the least squares sense x'A x + b'x + c = 0%       weighting the i-th data by W(i)%%       X: given points Pi = [X(i,1), X(i,2)]%       W: weight W(i) for the i-th equation%       show: if (show == 1) make test output%%       z, a, b, alpha: parameters for found ellipse%       err: error indication%         if (err == 1), not an ellipse%         if (err == 0), ok  if (nargin < 2), W = ones(size(X,1), 1); end;  if (nargin < 3), show = 0; end;  [U S V] = svd(diag(W) * [X(:,1).^2  X(:,1).*X(:,2) X(:,2).^2 ...                          X(:,1) X(:,2) ones(size(X(:,1)))]);  u   = V(:,6);  [z, a, b, alpha, err] = ellipse_params (u, show);end % algellipse