How to use the sum of all the iterations of a value calculated in a for-loop to calculate another value within the same loop?

Question

Jessica Hale 2022-9-20

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1808835-how-to-use-the-sum-of-all-the-iterations-of-a-value-calculated-in-a-for-loop-to-calculate-another-va

编辑： Dyuman Joshi 2022-9-20

Hi, I am trying to calculate the species mass fractions (Wi) within a stream by dividing the species flow rate (Mi) by the overall mass flow rate (sum of all values of Mi). I have managed to calculate and save all the mass flow rates (mi), but I'm struggling with summing all those values to get the overall stream mass flow rate. Any help would be greatly appreciated.

for i = 1:50
    Mi = M(i)*n(i); % species mass flow rate (g/h)
    mi(i) = Mi;
    Xi = n(i)/sum(n); % species mole fraction (no unit)
    xi(i) = Xi;
    Wi = Mi/sum(mi); % species mass fraction (no unit) - this is the denominator I'm struggling with
    wi(i) = Wi; 
end

4 个评论
显示 2更早的评论隐藏 2更早的评论

Dyuman Joshi 2022-9-20

It's not a bit clear to me what you are trying to do, can you an example with a set of data?

Jessica Hale 2022-9-20

So sorry, I meant something like this:

M = [2 3]
n = [8 9]
Mi_1 = M(1)*n(1)
Mi_2 = M(2)*n(2)
mi = [Mi_1 Mi_2]
mi_total = sum(mi)
Wi_1 = Mi_1/mi_total
Wi_2 = Mi_2/mi_total
wi = [Wi_1 Wi_2]

But I want to do this for when M and n are 50x1 arrays, and then calcuate Mi_1,..., Mi_50 and Wi_1,..., Wi_50 in a for loop.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Dyuman Joshi 2022-9-20

编辑：Dyuman Joshi 2022-9-20

Is using a loop necessary?

If yes, then my comment above should work -

M = [2 3];
n = [8 9];
for i = 1:2
    mi(i) = M(i)*n(i); % species mass flow rate (g/h)
end
mi
mi = 1×2
    16    27
wi=mi/sum(mi)
wi = 1×2
    0.3721    0.6279

If no, then you can do without loop as well

mi1=M.*n
mi1 = 1×2
    16    27
wi1=mi1/sum(mi1)
wi1 = 1×2
    0.3721    0.6279

Verification, with the code you provided

Mi_1 = M(1)*n(1);
Mi_2 = M(2)*n(2);
Mi = [Mi_1 Mi_2]
Mi = 1×2
    16    27
Mi_total = sum(Mi);
Wi_1 = Mi_1/Mi_total;
Wi_2 = Mi_2/Mi_total;
Wi = [Wi_1 Wi_2]
Wi = 1×2
    0.3721    0.6279