These options allow one to read an external .ufm file into the internal matrix, either
(i) “as is”
(ii) as its transpose (Tij becomes Tji)
(iii) as a compressed/expanded/recoded matrix whereby zones are transformed
(iv) as an aggregated version of a stacked input matrix (i.e., with all levels summed to create a single square matrix)
(v) as a single level from an input stacked matrix
(vi) by “pasting” an external square matrix into a single level of an internal stacked matrix
Some, but not all, of these options may also be applied to the internal matrix. In effect the internal matrix is first copied to a “scratch” external matrix, from which the internal matrix is re-created according to the various options above.
Options (i) and (ii) are self-explanatory; indeed case i) is what happens automatically when one or more input .ufm matrix files are initially defined in a run of MX; see 10.3.1. Case (ii) follows the same general conditions as described in 10.8.4, e.g., the matrix must be either square or composed of a stacked/blocked set of square matrices.
Case (iii) requires further explanation since it is the main mechanism within MX by which the structure of the zones may be “edited”, i.e. the number of rows and columns may be altered as opposed to “editing” individual cells. It also differs from, i) and ii) in that the changes may be applied to each level of a stacked matrix whereas the first two methods apply only to “square” matrices.
Cases (iv) to (vi) apply to various operations involving stacked matrices as described in more detail below, Section 10.4.3.