How to accumulate values into a variable using for loops?

Question

NH 2013-4-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/72195-how-to-accumulate-values-into-a-variable-using-for-loops

Hello,

I have an array that contains 1597 values. Let's call that X. I want to create a second array, Y, that should act as the following:

Y(1) = (X(1) + X(2))/(constant)

Y(2) = (X(2) + X(3))/(constant) + Y(1)

Y(3) = (X(3) + X(4))/(constant) + Y(2)

Y(4) = (X(4) + X(5))/(constant) + Y(3)

..and so on, until the last one:

Y(1596) = (X(1596) + X(1597))/(const) + Y(1595)

My code, which does not return an error, but also does not produce the correct values for Y, is as follows:

Y = zeros(1,length(X)-1);
Y(1) = (X(1)+X(2))/(constant);
i = 1:length(X);
for c = 1:length(X)-2
    Y(c+1) = (X(c+1)+X(c+2))/(constant) + Y(i(c));
end

As stated above, the results I'm getting are not accurate (I'm comparing with results obtained through Excel, which are definitely correct). If anyone can please tell me where I'm going wrong, I would greatly appreciate it. If this description isn't clear enough, please let me know and I will try to clarify. Any help is greatly appreciated.

Thanks.

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Answer 1

Yao Li 2013-4-16

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/72195-how-to-accumulate-values-into-a-variable-using-for-loops#answer_82361

编辑：Yao Li 2013-4-16

在 MATLAB Online 中打开

Y(c+1) = (X(c+1)+X(c+2))/(constant) + Y(c);

Also, actually, you don't need the parameter i.

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Yao Li 2013-4-16

I think the output of Matlab shoulb be close to that of Excel, but the precisions are different. Maybe you can try other data format in Matlab or Excel since the value are too small. It's better to give an example to show the differences.

NH 2013-4-16