how to add to matrix of different dimensions

Ex: a=3*10; b=b+a; in the first iteration b is getting 3*10, next iteration if a is 7*10 getting error. how to rectify

[Walter Roberson]

What do you want the result to be when you add two matrix of different sizes?

[rajesh kumar]

in the first iteration process i will got a=3*10 matrix, i have written initially b=0; b=b+a; i am getting b=3*10, in the next iteration process i am getting a=7*10 size, now b=b+a is getting error. how to rectify

[KSSV]

When you are adding b = b+a, the dimensions of b and a are same..as there is no error. How later a became 7*10? We cannot comment unless we see your complete code with all variables defined.

[Jan]

@rajesh kumar: I assume that "3*10" means a [3 x 10] matrix, and not 30.

b = rand(3, 10)
a = rand(7, 10)

What do you expect as output of a addition of these two variables? It is neither defined in Matlab nor mathematically.

[rajesh kumar]

actually in the image shown category 1 i.e first four rows i sorted, ok. next category 2 i.e next four rows i sorted, i want to combine i.e not addition to come original size.

[Walter Roberson]

If b is 3 x 10 and a is 4 x 10 and you want to combine into a 7 x 10 array, then

b = [b; a];