How can I concatenate vectors to create non-rectangular matrices in MATLAB?

Question

Is there a way to create non-rectangular matrices? For example, if I have a matrix a=[6 8 10] and another matrix b=[1 5], can I vertically concatenate them in order to obtain [6 8 10] in one row and [1 5] in another?

Answer 1

The direct answer is no. MATLAB does not support ragged or non-rectangular or non-square matrices. One way you could get around this is to make a cell array, where each cell is a vector of unequal lengths.

Something like:

a = [6 8 10];
b = [1 5];
c = cell(1,2);
c{1} = a;
c{2} = b;

celldisp(c)

c{1} =

     6     8    10

c{2} =

     1     5

Another way would be to create a matrix where those values that contain nothing get mapped to a preset number, like zero. Therefore, you could concatenate a and b to be a matrix such that it becomes [6 8 10; 1 5 0];. If this is what you prefer, you can do something like this:

a = [6 8 10];
b = [1 5];
c = zeros(2, 3);
c(1,1:numel(a)) = a;
c(2,1:numel(b)) = b;
disp(c)

 6     8    10
 1     5     0

A more comprehensive treatise on this particular topic can be found in gnovice's answer: How can I accumulate cells of different lengths into a matrix in MATLAB?

Another related answer was created by Jonas: How do I combine uneven matrices into a single matrix?