This available only for cell arrays.
[] - (Empty) Already an array
Numeric arrays can not store any other empty numeric arrays.
a = [1 2 3 4 5]
a(1) = [] % delete item 1
a = [1 2 3 [] 4 5] % a = [1 2 3 4 5] (concatenation of arrays)
c = cell(5)
isempty(c{1})
c(:,1) = {10}
c(:,3) = {20}
c =
[10] [] [20] [] []
[10] [] [20] [] []
[10] [] [20] [] []
[10] [] [20] [] []
[10] [] [20] [] []
