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.
