Fibonacci sequence for loop

Hey guys, I'm trying to write in Matlab Grader a function that returns a vector containing all elements of the Fibonacci sequence that are smaller or equal than m.

This is my code:

function fibonacciValue=fibonacciValue(m)
fibonacciValue(1) = 1;
fibonacciValue(2) = 1;
n=3;
while fibonacciValue(n-1) < m;
    fibonacciValue(n) = fibonacciValue(n-1)+fibonacciValue(n-2);
    n=n+1;
end     

The goal is to display the sequence up to the number equal to m; e.g. fibonacciValue(3)=[1,1,2,3] and fibonacciValue(10)=[1,1,2,3,5,8].

The problem is that it works for m=3, but not for higher numbers.

fibonacciValue(3)

fibonacciValue(10)

Does anybody knows how to fix this?

Thanks!!

Answer 1

[Stephen23]

Your while loop does not exit when you probably think it should...

Actually you will get the correct answer for m=3, 5, 8, 13, etc., as then the final loop iteration will generate exactly that value. But what happens when m is not one of the numbers in the fibonacci sequence? Then your loop will calculate one more iteration and return a vector one element longer than you want.

One simple solution is to use <= and remove the last vector element:

m = 10;
V = [1,1];
while V(end)<=m; % less-than or equal
    V(end+1) = sum(V(end-1:end));
end
V = V(1:end-1) % you need this!

[Leonardo Aldeghi]

function fibonacciValue=fibonacciValue(m)
fibonacciValue(1) = 1;
fibonacciValue(2) = 1;

fibonacciValue = [1,1];
while fibonacciValue(end)<=m; % less-than or equal
    fibonacciValue(end+1) = sum(fibonacciValue(end-1:end));
end
fibonacciValue = fibonacciValue(1:end-1); % you need 

I put your code in and worked perfectly! Thanks!!

[Jos (10584)]

Alternatively, you can take the n-2 value into account

while fibonacciValue(n-1)+fibonacciValue(n-2) < m
   % ...

and not have to remove the last element