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How to compute the sum term ?

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A Achbak
A Achbak on 21 Jan 2021
Commented: A Achbak on 22 Jan 2021
Hi, I hope you can help me in this problem :
Compute the sum term solution : which .
I don't need
% I have two solution U1 and U2
alpha = 0.6;
p = 0;
S = 0;
for n=2:50
p = p+1;
S = S+qnp*(U1-U2);
% Compute the new solution
U = 0.5*(U2+S);
% Overwrite the two solution
U1 = U2;
U2 = U;
% Resultat
The problem is
  • when n=2 then p=1, qnp=, and S = S+qnp*(U1-U2)=0+()*(U1-U2)= ()*(U1-U2)
It's Correct , then overwrite U1=U2 (i write it u2) and U2=U ( i write it u3)
  • When n=3 then p=2, qnp=, and S = S+qnp*(U1-U2) = ()*(U1-U2) + ()*(u2-u3).
It's not Correct because S = ()*(U1-U2) +()*(u2-u3) .
  • When n=4, then p=3 and the sum term is exactly : S = S+qnp*(U1-U2) = +qnp*(u3-u4)
which u3 and u4 has overwrited.
So, How can i compute the sum correctly ?

Accepted Answer

David Hill
David Hill on 22 Jan 2021
alpha = 0.6;
U(1)=1;%you need to specify U(1) and U(2)
for n=3:50
U(n+1) = (U(n)+S)/2;
  1 Comment
A Achbak
A Achbak on 22 Jan 2021
Thanks @David Hill yes it's working you use index of the solution U(1),U(2),...U(n)
But it's possible to no use index and just overwrite the solution U1=U2, U2=U which U is the new solution ? if you say yes, Can you say me how ?

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