Changing numbers summed together in for loop

I have a code below, which minuses one value from another and divides it by the defined time interval (dt).

This code works for the first iteration, as the time interval is 1, so it would be: Q_i+1 - Q_i.

However, I want this to change with the time interval, so that the next iteration does Q_i+2 - Q_i, then Q_i+3 -Q_i etc up until dt = 30.

Can anybody help me change the code so it does this?

dt = [1:1:30]; %increasing time intervals of interest up to Trw
nt = 28594;
for a = 1:length(dt)
Qtime = (Q_ots(2:end)- Q_ots(1:end-1))/dt(:,a)
Qt(a) = sum(Qtime)/nt
end 

Answer 1

[KSSV]

t = 1:1:30; %increasing time intervals of interest up to Trw
nt = 28594;
Qt = 0 ; 
for a = 1:length(dt)
Qtime = (Q_ots(a+1)- Q_ots(1)/t(a) ; 
Qt = QT+Qtime/nt ;
end