>>135774692D matrices are simply a result of encoding a linear map by expressing it over how some basis vectors over the domain map to some basis vectors over the range. The 2D is a remnant of having a domain by a range. If you want to upgrade a dimension, one rout is to add another dimension of domain (i.e. multilinear). Alternatively, you could add a dimension to the range, but this is trivial. and can be converted back to a 2D matrix.
