You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: rotate.m
    path of file: ./repos/spm12/external/fieldtrip/inverse/private
    
    the code of the file until where you have to start completion: function [H] = rotate(f)

% ROTATE returns the homogenous coordinate transformation matrix
% corresponding to a rotation around the x, y and z-axis. The direction of
% the rotation is according to the right-hand rule.
%
% Use as
%   [H] = rotate(R)
% where
%   R       [rx, ry, rz] in degrees

    
function [H] = rotate(f)

% ROTATE returns the homogenous coordinate transformation matrix
% corresponding to a rotation around the x, y and z-axis. The direction of
% the rotation is according to the right-hand rule.
%
% Use as
%   [H] = rotate(R)
% where
%   R       [rx, ry, rz] in degrees
%   H       corresponding homogenous transformation matrix
%
% Note that the order in which the rotations are performs matters. The
% rotation is first done around the z-axis, then the y-axis and finally the
% x-axis.

% Copyright (C) 2000-2005, Robert Oostenveld
%
% This program is free software; you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation; either version 2 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program; if not, write to the Free Software
% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

% This file is part of FieldTrip, see http://www.fieldtriptoolbox.org
% for the documentation and details.
%
%    FieldTrip is free software: you can redistribute it and/or modify
%    it under the terms of the GNU General Public License as published by
%    the Free Software Foundation, either version 3 of the License, or
%    (at your option) any later version.
%
%    FieldTrip is distributed in the hope that it will be useful,
%    but WITHOUT ANY WARRANTY; without even the implied warranty of
%    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
%    GNU General Public License for more details.
%
%    You should have received a copy of the GNU General Public License
%    along with FieldTrip. If not, see <http://www.gnu.org/licenses/>.
%
% $Id$

if numel(f)~=3
  ft_error('incorrect input vector');
end