% FITPLANE - solves coefficients of plane fitted to 3 or more points%% Usage:   B = fitplane(XYZ)%% Where:   XYZ - 3xNpts array of xyz coordinates to fit plane to.   %                If Npts is greater than 3 a least squares solution %                is generated.%% Returns: B   - 4x1 array of plane coefficients in the form%                b(1)*X + b(2)*Y +b(3)*Z + b(4) = 0%                The magnitude of B is 1.%% See also: RANSACFITPLANE% Copyright (c) 2003-2005 Peter Kovesi% School of Computer Science & Software Engineering% The University of Western Australia% http://www.csse.uwa.edu.au/% % Permission is hereby granted, free of charge, to any person obtaining a copy% of this software and associated documentation files (the "Software"), to deal% in the Software without restriction, subject to the following conditions:% % The above copyright notice and this permission notice shall be included in % all copies or substantial portions of the Software.%% The Software is provided "as is", without warranty of any kind.% June 2003function B = fitplane(XYZ)    [rows,npts] = size(XYZ);        if rows ~=3    error('data is not 3D');  end    if npts < 3    error('too few points to fit plane');  end    % Set up constraint equations of the form  AB = 0,  % where B is a column vector of the plane coefficients  % in the form   b(1)*X + b(2)*Y +b(3)*Z + b(4) = 0.    A = [XYZ' ones(npts,1)]; % Build constraint matrix    if npts == 3             % Pad A with zeros    A = [A; zeros(1,4)];   end  [u d v] = svd(A);        % Singular value decomposition.  B = v(:,4);              % Solution is last column of v.