average every nth column in matrix with n getting larger in matlab

main.m
%Generate random matrix A with dimensions n x m
n = 10; %number of rows
m = 20; %initial number of columns
A = rand(n,m);

%Define the value of increment k
k = 2;

%Initialize the new matrix B 
B = zeros(n,fix(m/k));

%Iterate through the columns, averaging every k columns
for i = 1:fix(m/k)
    %Define column range to average
    col_range = (i-1)*k+1:i*k;
    %Average the values in the column range
    B(:,i) = mean(A(:,col_range),2);
end
445 chars
19 lines