How can I update initial value of an array in a for loop?

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suman Dhamala
suman Dhamala 2018-2-10
编辑： Greg 2018-2-10
a(1)=0.1, a(2)= 0.11;
for k=2:10^10
a(k+1)= a(k)+a(k-1)+.....
if a(k+1)> 5.0
Up = k ;
end
end.
It takes a lot of memory as iteration number is very high.
How can I update the initial value like a(3)=a(2); a(1)=a(2)
and find new a(3) till my condition is satisfied.
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Greg
Greg 2018-2-10
编辑：Greg 2018-2-10
I'm assuming the initial conditions (first two values), or the threshold change? Otherwise, this is a trivial problem and k never changes.
Greg
Greg 2018-2-10
My comment on preallocation comes from the ambiguity of a(k+1)= a(k)+a(k-1)+..... This made me think you needed the entire vector.

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Greg
Greg 2018-2-10
编辑：Greg 2018-2-10
Use 3 separate variables, with a slight fix to the value assignment you suggested in the question. Also, throw a break inside the condition - or better, use a while loop (with the counter).
one = 0.1;
two = 0.11;
for k=2:10^10
three = one + two;
if three > 5.0
break
end
two = three;
one = two;
end

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