trying to make a new array that is the sum of the previous entry for an unknown length

I am writing a code that adds the length of a previous element of an array into a new array with an unknown length but am having problems. Hypothetically, say i have an array of [1 2 3 4], I want the new array I am creating to be [1, 3, 6, 10]. In this code history is my array I have already found and i am trying to save the new array into playVal. I am currently getting the error message "Array indices must be positive integers or logical values," and I am too inexperienced with coding to be able to think up a solution.

n = length(history);
count = 1;
playVal = [];
while length(playVal) <= n 
    playVal(end+1) = history(count) + history(count - 1);
    count = count + 1;
end

[Torsten]

Shouldn't the new array be [1, 3, 5, 7] instead of [1, 3, 5, 9] ?

[Jacob]

Also messed up on the new array it should be [1 3 6 10] because it is [1, 2+1, 3+(2+1), 4+3+(2+1)]

[Torsten]

Then simply set

playVal = cumsum(history)

[Jacob]

Cant believe it was that simple, thank you.

Answer 1

[Voss]

history = [1 2 3 4];

One way:

n = length(history);
playVal = zeros(1,n);
if n > 0
    playVal(1) = history(1);
    for count = 2:n
        playVal(count) = history(count) + playVal(count-1);
    end
end

playVal

playVal = 1×4

1 3 6 10

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A simpler alternative:

playVal = cumsum(history)

playVal = 1×4

1 3 6 10

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[Jacob]

thank you!

[Voss]

You're welcome!