Constructing a block diagonal matrix using the contents of a cell

Question

James 2011-12-13

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https://ww2.mathworks.cn/matlabcentral/answers/23824-constructing-a-block-diagonal-matrix-using-the-contents-of-a-cell

Hi, I have created a structure which contains, say, four vectors of different lengths. So, for example:

AA=[98x1 double] [20x1 double] [98x1 double] [20x1 double]

I then use these vectors to pick out certain elements of a non-full matrix A, so, for instance (A(AA{1},AA{1}).

I was looking for a quick way to create a block diagonal matrix, with the entries, (A(AA{1},AA{1}) in the entry (1,1), (A(AA{2},AA{2})in the entry (2,2), (A(AA{3},AA{3}) in the entry (3,3) and (A(AA{4},AA{4}) in the entry (4,4) (ie: on the diagonals), with zeros obviously in the other positions. Is anyone aware of the best way to achieve this? I am unsure how to `tell' Matlab the dimension of the zero's in the block matrix, which will differ on an entry-by-entry basis.

Any help would be much appreciated.