MATLAB: Converting only certain cells to a matrix

Question

consider the following example

    a = { rand(1877958,7); rand(1251972,7); rand(4564357,7) };

i want only the first two cells to be converted to a matrix. i know that the rows are not the same but the remaining rows can be filled with zeros. how can i do that in such a way so that the output has 14 columns meaning the matrices are put adjacent to each other. thanks

Answer 1

a = { rand(1877958,7); rand(1251972,7); rand(4564357,7) };
n=max(cellfun(@(x) size(x,1) , a(1:2)) )
b=cell2mat(cellfun(@(x) [x;zeros(n-size(x,1),7)],a(1:2)','un',0));