Check out the documentation for cell2mat at http://www.mathworks.com/help/matlab/ref/cell2mat.html and in particular the example. In your case, the matrices have a different number of rows so cannot be concatenated in this way. But, if your cell array mydata was a column (rather than a row) with the same two elements, then yes it could be concatenated because each matrix has the same number of columns
mydata = cell(2,1);
mydata{1} = zeros(10,11);
mydata{2} = ones(5,11);
mtx = cell2mat(mydata);
