calc_Mq

% Multiplication matrix for quaternions
 q p = M(q)*p, see PCV (8.45)

 Usage:
    M = calc_Mq(q)

   q - double 4x1, quaternion

   M - double 4x4, Multiplication matrix for quaternions

 Wolfgang Förstner
 wfoerstn@uni-bonn.de 

 See also calc_Mq_comm, calc_R_from_opq_kraus, calc_r_phi_from_R,
 calc_Rot_ab, calc_Rot_q, calc_Rot_r, calc_Rot_rod, calc_Rot_rp,
 calc_opq_from_R_Kraus

0001 %% Multiplication matrix for quaternions
0002 % q p = M(q)*p, see PCV (8.45)
0003 %
0004 % Usage:
0005 %    M = calc_Mq(q)
0006 %
0007 %   q - double 4x1, quaternion
0008 %
0009 %   M - double 4x4, Multiplication matrix for quaternions
0010 %
0011 % Wolfgang Förstner
0012 % wfoerstn@uni-bonn.de
0013 %
0014 % See also calc_Mq_comm, calc_R_from_opq_kraus, calc_r_phi_from_R,
0015 % calc_Rot_ab, calc_Rot_q, calc_Rot_r, calc_Rot_rod, calc_Rot_rp,
0016 % calc_opq_from_R_Kraus
0017 
0018 function M = calc_Mq(q)
0019 
0020 a = q(1);
0021 b = q(2);
0022 c = q(3);
0023 d = q(4);
0024 
0025 M=[ a -b -c -d; ...
0026     b  a -d  c; ...
0027     c  d  a -b; ...
0028     d -c  b  a
0029     ];