NMRPipe Processing Functions
HA: Sequential Hadamard Transform.
Input is zerofilled to a required power of two.
HA applies a Hadamard transform to the vectors in the data. This transform is a relative of the Fourier transform, and is sometimes used as an alternative to a Fourier transform for signal processing and enhancement methods. For a data vector with 2^m points, the Hadamard transform is defined in terms of a scale factor and a transform matrix H, which is a matrix of (2^m) x (2^m) values, which are all either 1 or -1. So, If input data is complex, the real and imaginary parts are treated separately, since the Hadamard transform matrix is all-real. Since the Hadamard transform matrix is defined in terms of powers of two, it requires that the input data is an exact power of two in size. Therefore, if needed, input data is automatically zero-filled to the nearest power of two before the transform is applied.
This flag scales the result by 1/N, where N is the number of points in the transformed vector.
The HA function toggles the NDFTFLAG to 1 or 0, depending on whether the input is time-domain or frequency domain, respectively.