cell array to matrix
C = {[1], [2 3 4];
[5; 9], [6 7 8; 10 11 12]}
C=2×2 cell array
{[ 1]} {[ 2 3 4]}
{2x1 double} {2x3 double}
A = cell2mat(C)
A = 3×4
1 2 3 4
5 6 7 8
9 10 11 12