# x1,x2,x3,x4
[
   [  1,  0,  0,  0,  0 ]
   [  0,  1,  0,  0,  0 ]
   [  0,  0,  1,  0,  0 ]
   [  0,  0,  0,  1,  0 ]
   [  0,  0,  0,  0,  1 ]
]

# x1,-x2,x3,x4+1/2
[
   [  1,  0,  0,  0,  0 ]
   [  0, -1,  0,  0,  0 ]
   [  0,  0,  1,  0,  0 ]
   [  0,  0,  0,  1, 0.5 ]
   [  0,  0,  0,  0,  1 ]
]

# x1+1/2,x2+1/2,x3,x4
[
   [  1,  0,  0,  0, 0.5 ]
   [  0,  1,  0,  0, 0.5 ]
   [  0,  0,  1,  0,  0 ]
   [  0,  0,  0,  1,  0 ]
   [  0,  0,  0,  0,  1 ]
]

# x1+1/2,-x2+1/2,x3,x4+1/2
[
   [  1,  0,  0,  0, 0.5 ]
   [  0, -1,  0,  0, 0.5 ]
   [  0,  0,  1,  0,  0 ]
   [  0,  0,  0,  1, 0.5 ]
   [  0,  0,  0,  0,  1 ]
]

