If you want the value of sumv stored at each iteration of your k loop, index it to create a vector from it:
sumv(1)=0;
n=0;
an=0;
for k=1:120
an=.68+sumv(k)-(.68+sumv(k)).*.0693;
sumv(k+1)=an;
end
figure(1)
plot(sumv)
grid
You could preallocate by putting:
sumv = zeros(1,121);
in place of:
sumv(1)=0;
That’s good programming practice, but here it likely doesn’t make much of a difference in terms of speeding up your loop. I decided to keep with your original construction rather than preallocate.
