# How to increase the size of a matrix within for loop

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Hello
There is a for loop in my code.
imagine i obtain value 1 after the first iteration, so it would be my first array in the matrix CM--->so CM=[1]
then in the second iteration i obtain: [1 0.214; 0.214 1] which i want to be added to the matrix CM as
CM= [1 0 0;
0 1 0.214;
0 0.214 1]
then in the third iteration i obtain: [1 0 0; 0 1 0.0013; 0 0.0013 1] , so the matrix CM should become:
CM= [1 0 0 0 0 0;
0 1 0.214 0 0 0;
0 0.214 1 0 0 0;
0 0 0 1 0 0;
0 0 0 0 1 0.0013
0 0 0 0 0.0013 0]
and so forth.
How can i formulate this? Any help is highly appreciated.

Steven Lord on 13 May 2021
Consider creating a cell array to store the pieces you want to be placed on the main diagonal. When you want to assemble the matrix call blkdiag, creating a comma-separated list of input arguments using the cell array.
C = {1, [1 2;2 1], [1 2 3; 2 3 1; 3 1 2]};
P = blkdiag(C{1})
P = 1
Q = blkdiag(C{1:2})
Q = 3×3
1 0 0 0 1 2 0 2 1
R = blkdiag(C{1:3})
R = 6×6
1 0 0 0 0 0 0 1 2 0 0 0 0 2 1 0 0 0 0 0 0 1 2 3 0 0 0 2 3 1 0 0 0 3 1 2
S = blkdiag(C{:})
S = 6×6
1 0 0 0 0 0 0 1 2 0 0 0 0 2 1 0 0 0 0 0 0 1 2 3 0 0 0 2 3 1 0 0 0 3 1 2
Pooneh Shah Malekpoor on 13 May 2021
Great! Could you please tell me how can i store each of the cell arrays in the matrix C? i mean how can i ask matlab to store [ 1 2;2 1] in the second array of C, then store [1 2 3; 2 3 1; 3 1 2] in the third array and so forth?
C = {1, [1 2;2 1], [1 2 3; 2 3 1; 3 1 2]}