How to concatenate matrices when some of them can be empty?

I have 10 matrices, each of them would either have a size of n by 12, or is empty. For example: T1 can be a matrix with a size of 100 x 12, but it can also be []. The same thing goes true for T2, ... T10.

What is the best way to put them together like the below?

vertcat(T1, T2, T3, ... T10)

Many thanks!

Answer 1

[Image Analyst]

I'd do it almost like you. This works fine and has 9 rows because T7 is empty.

T1 = rand(1, 12);
T2 = rand(1, 12);
T3 = rand(1, 12);
T4 = rand(1, 12);
T5 = rand(1, 12);
T6 = rand(1, 12);
T7 = []; 
T8 = rand(1, 12);
T9 = rand(1, 12);
T10 = rand(1, 12);
tallerMatrix = vertcat(T1, T2, T3, T4, T5, T6, T7, T8, T9, T10)

Answer 2

[Voss]

make the empty matrices 0-by-12, then you can vertcat them like normal.

if isempty(T2)
    T2 = zeros(0,12);
end
% and so on

[Leon]

Thanks, but now I have an extra row of zeros, which is not what I want.

[Edric Ellis]

zeros(0,12) generates an empty matrix with the right number of columns. When you vertcat this, it disappears. Like this:

T1 = rand(1, 4);
T2 = zeros(0, 4);
T3 = 10 + rand(1, 4);
vertcat(T1, T2, T3)

ans = 2×4

0.0375 0.3622 0.0174 0.9187 10.5569 10.8928 10.4045 10.8303

Making the right number of columns is not strictly necessary in this case, since vertcat knows how to ignore [] which is of size [0 0].

[Leon]

Many thanks!

Interesting to hear the behavior of zeros when vertcating.