[ot][spam][random][crazy][random][crazy]

[Undescribed Horrific Abuse, One Victim & Survivor of Many]

this is a 4x4 inverse dft matrix:

array([[ 0.25-0.j  ,  0.25-0.j  ,  0.25-0.j  ,  0.25-0.j  ],
       [ 0.25-0.j  ,  0.  +0.25j, -0.25+0.j  , -0.  -0.25j],
       [ 0.25-0.j  , -0.25+0.j  ,  0.25-0.j  , -0.25+0.j  ],
       [ 0.25-0.j  , -0.  -0.25j, -0.25+0.j  ,  0.  +0.25j]])

each column is a vector in the complex plane of length 1/4 rotating by
increasing multiples of 90 degrees. So is each row.