How to buffer old columns in a matrix when new columns are added

I'm writing a loop where I'm continually adding to an m x n matrix called histoMat on each iteration with a row vector called reposit. reposit is re-initialized and differs in size from iteration to iteration, but histoMat only grows, like so:

histoMat = [histoMat; reposit]

Unfortunately, I can't initialize the size of histoMat before the loop begins, since I don't know the maximum size of any single reposit row. As you can see, because reposit is very rarely the same size as it was the iteration before, I'm getting a vertcat dimension error when I try to append on to histoMat. For example, this will give me an error:

reposit = [1 2 3 4 5]
histoMat = [1 2 3]

histoMat = [histoMat; reposit]

Error using vertcat
Dimensions of matricies being concatenated are not consistent.

My question is: Is there any good way to buffer the bottom of histoMat with zeros whenever needed in order to avoid this? Here's an ideal example of what I'd like to accomplish:

reposit = [1 2 3 4 5]
histoMat = [1 2 3]
histoMat = [histoMat; reposit]

histoMat = [1 2 3 0 0 
            1 2 3 4 5]

Answer 1

[James Tursa]

Append reposit this way:

histoMat(end+1,1:numel(reposit)) = reposit;

[Jack Olmstead]

This works perfectly. Thank you!