How to make columns the same size

My data has two columns (A and B). Column A has a number of rows. Column B has fewer rows than A. How can I make column B have the same number of rows as A ? also, These rows must be filled with the average of the row data in column A.

Answer 1

[Jos (10584)]

A solution:

A = [1 3 ; 2 4 ; 5 7]
B = [10 11 12 ; 13 14 15]
newB = repmat(mean(A,2), 1, size(B,2)) 
newB(1:size(B,1),:) = B