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

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Leon
Leon am 15 Dez. 2021
Kommentiert: Leon am 15 Dez. 2021
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!

Akzeptierte Antwort

Image Analyst
Image Analyst am 15 Dez. 2021
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)

Weitere Antworten (1)

Voss
Voss am 15 Dez. 2021
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
  3 Kommentare
Edric Ellis
Edric Ellis am 15 Dez. 2021
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
Leon am 15 Dez. 2021
Many thanks!
Interesting to hear the behavior of zeros when vertcating.

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