Convert a cell with structures into a matrix

Hi, does anyone know how to could I go from the information I have stored in the variable A to what I have in the variable matrix?

% Input data.
A = cell(3,1);
A{1}.data = [1 2 3];
A{1}.a = 0;
A{2}.data = [4 5 6];
A{2}.a = 1;
A{3}.data = [7 8 9];
A{3}.a = 3;

% Result to obtain.
matrix = [1 2 3; 4 5 6; 7 8 9];

Answer 1

[David Hill]

m=[];
for k=1:3
    m=[m;A{k}.data];
end

[Stephen23]

@David Hill: you forgot this:

https://www.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html

Answer 2

[Stephen23]

Rather than inefficiently storing lots of scalar structures in a cell array, you should just use one efficient non-scalar array, then your task is trivial:

S(1).data = [1 2 3];
S(1).a = 0;
S(2).data = [4 5 6];
S(2).a = 1;
S(3).data = [7 8 9];
S(3).a = 3;
M = vertcat(S.data) % this is all you need!

M = 3×3

1 2 3 4 5 6 7 8 9

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

Note that you can also convert that unfortunate cell array of scalar structures to one structure array:

S = [A{:}];