MATLAB: How to update initial value of an array in a for loop

update initial value in a loop

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.

Best Answer

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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