--- /dev/null
+function rz = vecrotz(angle)
+%
+% VECROTZ: Transformation matrix for a rotation around the z axis.
+%
+% Calling Sequence:
+%
+% rz = vecrotz(angle);
+%
+% INPUT:
+%
+% angle : rotation angle defined in radians
+%
+% OUTPUT:
+%
+% rz : (4x4) Transformation matrix.
+%
+%
+% Description:
+%
+% Return the (4x4) Transformation matrix for a rotation about the z axis
+% by the defined angle.
+%
+% The matrix is:
+%
+% [ cos(angle) -sin(angle) 0 0]
+% [ -sin(angle) cos(angle) 0 0]
+% [ 0 0 1 0]
+% [ 0 0 0 1]
+%
+% Examples:
+%
+% Rotate the NURBS line (0.0 0.0 0.0) - (3.0 3.0 3.0) by 45 degrees
+% around the z-axis
+%
+% line = nrbline([0.0 0.0 0.0],[3.0 3.0 3.0]);
+% trans = vecrotz(%pi/4);
+% rline = nrbtform(line, trans);
+%
+% See also:
+%
+% nrbtform
+%
+% Copyright (C) 2000 Mark Spink
+%
+% 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, see <http://www.gnu.org/licenses/>.
+
+sn = sin(angle);
+cn = cos(angle);
+rz = [cn -sn 0 0; sn cn 0 0; 0 0 1 0; 0 0 0 1];
+
+end