To find average of the frames extracted from a video

I wrote a code for extracting image frames from a video.But i am unable to get average of these extracted frames.can anyone please help me? my code is

clc;

close all;

clear all;

mov=aviread('viptraffic_original.avi');

info=aviinfo('viptraffic_original.avi');

k=info.NumFrames;

for i=1:k

m=aviread('viptraffic_original.avi',i);

f=frame2im(m);

figure,imshow(f);

end.