Fibonnaci until a ratio is achieved between adjacent values. (2024)

Hi Milton,

I understand that you are facing an error while implementing the Fibonacci Sequence. I have investigated the attached code and found that the issue is due to the condition in the while loop. To be clear, let us focus on this section of your code:

When the control reaches the while loop, and the condition is evaluated for the first iteration, it attempts to access x(3), whereas x is of size 2, meaning it only has two elements. To address this, you can tweak your code as per the following format:

I hope this helps.

clear, clc

format default

% Create a program that accepts the first two numbers of a Fibonacci

% sequence as user input, then calculates additional values in the sequence

% until the ratio of adjacent values converges to within 0.001.

% Define the inputs.

fib_first = input('Please enter the first number: ');

fib_second = input('Please enter the second number: ');

% Set an upper limit for the number of Fibonacci numbers to calculate.

max_iterations = 1000;

% Define a vector with enough space for the Fibonacci sequence.

x = zeros(1, max_iterations);

x(1) = fib_first;

x(2) = fib_second;

i = 3;

while abs(x(i-1)/x(i-2) - x(i-2)/x(i-3)) > 0.001

x(i) = x(i-1) + x(i-2);

i = i + 1;

if i > max_iterations

disp('Convergence not achieved within the specified limit.');

break;

end

end

% Trim the x vector to remove unused elements.

x = x(1:i-1);

% Display the Fibonacci sequence.

disp('Fibonacci sequence:');

disp(x);

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  https://support.mathworks.com/matlabcentral/answers/2016256-fibonnaci-until-a-ratio-is-achieved-between-adjacent-values#comment_2872241

Open in MATLAB Online

>> fibseq = [0 1 1 2 3 5 8 13 21 34 55];

>> abs(diff(fibseq(1:end-1)./fibseq(2:end)))

ans =

1.0000 0.5000 0.1667 0.0667 0.0250 0.0096 0.0037 0.0014 0.0005

function seq = fibo

isperfect = @(x)(int64(sqrt(x)) .^ 2 == x);

isfib = @(x)(isperfect(5 * x.^2 + 4) | isperfect(5 * x.^2 - 4));

f(1) = input('1st Fibonacci Number:');

if ~isfib(f(1)), error('%d is not a Fibonacci number',f(1));

end

f(2) = input('2nd Fibonacci Number:');

if ~isfib(f(2)), error('%d is not a Fibonacci number',f(2));

end

fibseq = [0 1 1 2 3 5 8 13 21 34 55];

if f(2) >= fibseq(end), seq = f;

else seq = fibseq(fibseq >= f(1));

end