4 Point WHT
Four Point Walsh Hadamard transform.
The 4 point Walsh Hadamard transform is computed by first applying two 2-point WHTs to the input data and then forming the sum and difference of the 2 sum terms and the sum and difference of the two difference pairs.
Matrix equivalent of the 4 point WHT. While the matrix form requires more computation than successively applying 2 point transforms. It has use for understanding some of the mathematical properties of the WHT.