Mustard convolution
R = mustard(f, g, mu, H)
R = mustard(f, g, mu, H) returns the so-called 'Mustard' convolution of f and g. This is the convolution equivalent to pointwise multiplication of the Fourier transforms of f and g. It is dependent on the definition of the Fourier transform. This function assumes a one-sided QFT as computed by qfft and qfft2 using a transform 'axis' mu and a handedness H as defined in the parameter profiles of the transforms. The computation performed by the mustard function does not use Fourier transforms: it is computed using convolutions, but these convolutions differ according to the equivalent transform axis and handedness.
This code handles one dimensional or two dimensional arrays f and g according to the parameters supplied. If they are vectors, they must be both row or both column vectors.