This function will assemble a large matrix out of a number of smaller ones m1, m2, etc., according to a pattern P. If P is 3x5, then the large matrix will be three times as tall as the small ones, and five times as wide. The small matrices must always have the same dimensions as one another.
The pattern P will be a matrix of integers, each no larger than the number of small matrices provided. Each element in P identifies the small matrix that should be used to fill the corresponding positions in the large matrix. A zero in P indicates that the corresponding patch of the large matrix should be filled with zeros, a 1 indicates it should be filled with m1, etc. Each small matrix may be used more than once, or not at all.
For example, if P = [1 0; 1 2], m1 = eye(2), and m2 = ones(2), then the large matrix M should be
M = 1 0 0 0 0 1 0 0 1 0 1 1 0 1 1 1