How to modify an array's elements using another element?

I need to write a for loop that will set each array element in bonusScore to the sum of itself and the next element (except for the last element which stays the same). Why why does my code yield these (incorrect) output numbers? What should I do to fix my code?

function bonusScores = CombineScores(numberScores, userScores)
   for i = 1:numbersScores;
        userScores(1) = userScores(1) .* 2 + userScores(2);
        userScores(2) = userScores(2) .* 2 + userScores(3);
        userScores(3) = userScores(3) .* 2 + userScores(4);
        bonusScores = userScores;
   end
end

Input: CombineScores(4, [10, 20, 30, 40]) Output: ans = 1800, 1960, 1080, 40

[KALYAN ACHARJYA]

What results you are expecting on above-mentioned input?

Input: CombineScores(4, [10, 20, 30, 40])

[Matthew Burton]

I am expecting...

Output: [30, 50, 70, 40]

Thanks.

Answer 1

[Bruno Luong]

Fix code:

function bonusScores = CombineScores(numberScores, userScores)
for i = 1:numberScores-1
    userScores(i) = userScores(i) + userScores(i+1);
end
bonusScores = userScores;
end

Try

>> CombineScores(4, [10, 20, 30, 40])

ans =

      30    50    70    40

[Matthew Burton]

Thanks! Yes, I see... I just needed that last line.